Selectively thrusting propulsion units for aerial vehicles

ABSTRACT

Aerial vehicles may include propulsion units having motors with drive shafts that may be aligned at a variety of orientations, propellers with variable pitch blades, and common operators for aligning the drive shafts at one or more orientations and for varying the pitch angles of the blades. The common operators may include plate elements to which a propeller hub is rotatably joined, and which may be supported by one or more linear actuators that may extend or retract to vary both the orientations of the drive shafts and the pitch angles of the blades. Operating the motors and propellers at varying speeds, gimbal angles or pitch angles enables the motors to generate forces in any number of directions and at any magnitudes. Attributes of the propulsion units may be selected in order to shape or control the noise generated thereby.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/585,058, filed May 2, 2017, which is a continuation of U.S. patentapplication Ser. No. 15/083,123, filed Mar. 28, 2016, now U.S. Pat. No.9,663,236, the contents of which are incorporated by reference herein intheir entirety.

BACKGROUND

The use of unmanned aerial vehicles such as airplanes or helicoptershaving one or more propellers in a variety of applications isincreasingly common. Such vehicles may include fixed-wing aircraft, orrotary wing aircraft such as quad-copters (e.g., a helicopter havingfour rotatable propellers), octo-copters (e.g., a helicopter havingeight rotatable propellers) or other vertical take-off and landing (orVTOL) aircraft having one or more propellers. In most unmanned aerialvehicles, each of the propellers is powered by one or more rotatingmotors or other prime movers. The motors and propellers may be providedin propulsion units or modules that are physically joined to a frame orother structure of an unmanned aerial vehicle, e.g., a fuselage, a wing,or another portion of the vehicle, and electrically and/or mechanicallycoupled to one or more other systems or components, including but notlimited to computer-implemented control systems or modules. The neteffects of the operation of such propulsion units cause an unmannedaerial vehicle to travel in one or more directions and/or be held aloftthereby.

Propulsion units that are outfitted to unmanned aerial vehiclestypically include motors having shafts with fixed axes of orientationand propellers of fixed shapes, with the motors being configured torotate the propellers about the fixed axes of orientation by the shafts.Typically, a level of force (e.g., lift and/or thrust) provided by apropulsion unit having a motor and a propeller may be modified either byvarying a speed of the motor within a safe operating range (e.g., from afull stop condition to a maximum rotational or angular velocity), or byvarying pitch angles (or angles of attack) of blades of the propeller.Propulsion units that are outfitted to unmanned aerial vehicles aretypically not configured, however, to change either their respectivegimbal angles, e.g., angles of their axes of orientation about which thepropellers rotate, and along which the propulsion units are configuredto generate force, or the shapes of their respective propellers, duringoperation.

Sound is kinetic energy released by vibrations of molecules in a medium,such as air. In industrial applications, sound may be generated in anynumber of ways or in response to any number of events. For example,sound may be generated in response to vibrations resulting from impactsor frictional contact between two or more bodies. Sound may also begenerated in response to vibrations resulting from the rotation of oneor more bodies such as shafts, e.g., by motors or other prime movers.Sound may be further generated in response to vibrations caused by fluidflow over one or more bodies. In essence, any movement of molecules, orcontact between molecules, that causes a vibration may result in theemission of sound at a pressure level or intensity, and at one or morefrequencies. Properties of sound emitted by unmanned aerial vehiclesduring operation (e.g., sound pressure levels or frequency spectrums ofsuch sounds) are determined based on operating characteristics of theaerial vehicles, such as motor speeds or attributes of the propellersrotated thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1F are views of aspects of an aerial vehicle having oneor more embodiments of the propulsion units in accordance withembodiments of the present disclosure.

FIG. 2 is a block diagram of aspects of one system for operating anaerial vehicle having one or more embodiments of propulsion units inaccordance with the present disclosure.

FIG. 3 is a view of aspects of an embodiment of an aerial vehicle inaccordance with embodiments of the present disclosure.

FIGS. 4A through 4F are views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the presentdisclosure.

FIGS. 5A through 5D are views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the presentdisclosure.

FIGS. 6A and 6B are views of aspects of an embodiment of a propulsionunit in accordance with embodiments of the present disclosure.

FIGS. 7A and 7B are views of aspects of an embodiment of a propulsionunit in accordance with embodiments of the present disclosure.

FIGS. 8A and 8B are views of aspects of an embodiment of a propulsionunit in accordance with embodiments of the present disclosure.

FIGS. 9A through 9D are views of aspects of an aerial vehicle having oneor more embodiments of propulsion units in accordance with embodimentsof the present disclosure.

FIG. 10 is a flow chart of one process for operating an aerial vehiclehaving one or more embodiments of propulsion units in accordance withthe present disclosure.

FIG. 11 is a flow chart of one process for operating an aerial vehiclehaving one or more embodiments of propulsion units in accordance withthe present disclosure.

FIG. 12 is a flow chart of one process for operating an aerial vehiclehaving one or more embodiments of propulsion units in accordance withthe present disclosure.

DETAILED DESCRIPTION

As is set forth in greater detail below, the present disclosure isdirected to aerial vehicles having propulsion units that may beselectively operated in order to achieve a desired level of thrust orlift in a desired direction while emitting sounds at desired soundpressure levels (or intensities) and within desired frequency spectrums.The propulsion units may include one or more motors and one or morepropellers, along with components for varying a level and direction ofthrust or lift generated by such units in any number of ways, such as byvarying a gimbal angle of the propulsion units, varying a speed of amotor for rotating a propeller, or varying a pitch angle or shape of oneor more blades of the propeller. Because factors such as motor orpropeller speed, gimbal angle, pitch angle or blade shape have directeffects on forces generated by an operating propulsion unit, soundsradiated by the operating propulsion unit, or directions in which suchforces or sounds are directed, the capacity to manipulate such speeds,angles or shapes enables aerial vehicles having propulsion units of thepresent disclosure to control aspects of such forces (e.g., magnitudesor directions) or sounds (e.g., sound pressure levels or frequencyspectrums), including but not limited to regions in which such soundsare heard by one or more humans or other animals. Thus, where force(e.g., lift and/or thrust) in a given amount and/or direction isdemanded from a propulsion unit of the present disclosure or an aerialvehicle to which the propulsion unit is outfitted, speeds of a motor orpropeller, gimbal angles, pitch angles or blade shapes may beindividually adjusted, as necessary, to generate and radiate a specificor desired sound in a selected direction while satisfying a demand forthe force. Where an aerial vehicle includes two or more of suchpropulsion units, each of the propulsion units may be independentlyoperated to generate specific or desired sounds while generating forcesin specific amounts or directions.

In some embodiments of the present disclosure, the propulsion units mayinclude linear actuators that are configured to modify not only gimbalangles (e.g., the angles of the axes about which propellers are rotatedand, therefore, axes corresponding to directions of forces generatedthereby) of the propulsion units but also pitch angles of the respectiveblades provided on each of the propellers. For example, a propulsionunit may include a hub or bearing ring to which blades of a propellerare rotatably mounted to a housing by their respective roots via one ormore pivotable connectors provided within the hub or bearing ring. Thepropulsion unit may also include a motor assembly having a motor towhich the propeller itself is mounted via a drive shaft that defines anaxis, and a planar element or plate provided in association with the hubor bearing ring. The planar element or plate may include a necked boreor other extension through which the drive shaft extends in slidingcontact, as well as one or more joints associated with the rotatableconnectors of the hub or bearing ring. The motor assembly may be mountedto a base within the housing by a gimbaling mechanism that enables themotor assembly to pivot freely about a point on the base while enablingthe motor to rotate the propeller about an axis defined by the motor.The pivotable connectors may be configured to cause the blades to pivotabout their respective roots to predetermined extents, determined as afunction of relative motion or distances between the planar element orplate and the hub or bearing ring. Thus, the planar element or plateacts a common operator which may be repositioned (e.g., along an axis ofa drive shaft of the motor) or reoriented (e.g., an angle of a planedefined by the planar element or plate, aligned substantiallyperpendicular to the drive shaft) in order to vary both pitch angles ofthe blades, and a gimbal angle of the propulsion unit, using the linearactuators.

In some embodiments, the linear actuators that are joined to the planarelement or plate may retract or be extended singularly or in concert.The retraction or extension of the linear actuators at specific pointson the planar element causes an angle of a plane of the planar elementor plate to vary. Where the drive shaft is slidably inserted into thenecked bore substantially perpendicularly, and where the motor assemblyis pivotably joined to a gimbaling mechanism on a base within thehousing, varying the angle of the plane of the planar elementnecessarily causes an angle of the axis or a gimbal angle of thepropulsion unit to vary accordingly. Additionally, the retraction orextension of the linear actuators may also cause a relative position ofthe hub or bearing ring to vary with respect to the planar element orplate, thereby repositioning the one or more pivotable connectors towhich the roots of the blades are mounted, and causing the pitch anglesof the blades to change accordingly. Preferably, the linear actuatorsmay be joined to the planar element or plate at three or more locationsabout the element or plate, thereby enabling such linear actuators topositively control both an angle of a plane of the planar element orplate, and a relative position of the planar element or plate, ensuringthat the pitch angles of the blades and the gimbal angle of thepropulsion unit are oriented as desired based on axial movements andangular alignments of a common operator, e.g., the planar element of theplate.

Accordingly, the propulsion units of the present disclosure may beoperated in a manner that specifically controls both a magnitude and adirection of a net force applied to an aerial vehicle by such propulsionunits, including not only magnitudes but also directions of forcessupplied by each of the respective propulsion units, based onindependent variables such as a motor or propeller speed, a gimbalangle, a blade pitch angle or a blade shape. Some embodiments mayinclude a plurality of linear actuators that may be operated separatelyor in concert to vary both the gimbal angle and the blade pitch anglesof such propulsion units accordingly by repositioning or realigning acommon operator. Some embodiments may also include motors that may beoperated at variable speeds and/or propellers that have blades withvarying shapes. The propulsion units of the present disclosure may beconfigured to modify one or more of such variables during operation,and, therefore, to control or shape the properties of sounds radiatingtherefrom.

Referring to FIGS. 1A through 1F, an aerial vehicle 110 having aplurality of propulsion units 130-1, 130-2, 130-3, 130-4 is shown. As isshown in FIG. 1A, each of the propulsion units 130-1, 130-2, 130-3,130-4 generates a force F₂₋₁, F₃₋₁, F₄₋₁ to counteract a weight ω₁₁₀ ofthe aerial vehicle 110 or other external forces acting on the aerialvehicle 110 (not shown). Each of the propulsion units 130-1, 130-2,130-3, 130-4 includes a motor assembly 160-1, 160-2, 160-3, 160-4 havingmotors and one or more actuators and components for controlling theoperation of the respective units 130-1, 130-2, 130-3, 130-4 withinhousings thereof, and a propeller 170-1, 170-2, 170-3, 170-4 providedexternal to such housings. The motor assemblies 160-1, 160-2, 160-3,160-4 and the propellers 170-1, 170-2, 170-3, 170-4 may be selectivelyoperated in order to determine, vary or select both the magnitudes andthe directions of the forces F₂₋₁, F₃₋₁, F₄₋₁ generated thereby.

The motors provided within the motor assemblies 160-1, 160-2, 160-3,160-4, may be any type or form of motor (e.g., electric,gasoline-powered or any other type of motor) capable of generatingsufficient rotational speeds of the corresponding propellers 170-1,170-2, 170-3, 170-4 to provide lift and/or thrust forces to the aerialvehicle 110 and any engaged payload, and to aerially transport theengaged payload thereby. For example, one or more of the motorassemblies 160-1, 160-2, 160-3, 160-4 may include a brushless directcurrent (DC) motor such as an outrunner brushless motor or an inrunnerbrushless motor.

Each of the motor assemblies 160-1, 160-2, 160-3, 160-4 may be similaror identical to one another, and may feature similar or identicalfeatures (e.g., power sources, numbers of poles, whether the motorsincluded therein are synchronous or asynchronous) or operationalcapacities (e.g., angular velocities, torques, operating speeds oroperating durations). Alternatively, two or more of the motor assemblies160-1, 160-2, 160-3, 160-4 of the aerial vehicle 110 may include motorshaving different features or capacities, based on an extent to which useof such motors or their corresponding propellers 170-1, 170-2, 170-3,170-4 is desired or required. Each of such motor assemblies 160-1,160-2, 160-3, 160-4 may be operated individually or in tandem with oneanother, for any purpose. For example, two or more of the motorassemblies 160-1, 160-2, 160-3, 160-4 and their corresponding propellers170-1, 170-2, 170-3, 170-4 may be operated to provide both lift andthrust, while two or more of the motor assemblies 160-1, 160-2, 160-3,160-4 and their corresponding propellers 170-1, 170-2, 170-3, 170-4 maybe operated to provide either lift or thrust, and in any desired angleor direction.

A view of internal components and other aspects of the propulsion unit130-4 is shown in FIG. 1B and FIG. 1C. For example, as is shown in FIG.1B and FIG. 1C, the propulsion unit 130-4 includes a housing 132-4, themotor assembly 160-4, the propeller 170-4 and a variable pitch hub180-4. The propeller 170-4 includes a plurality of blades 172-4 joinedto the variable pitch hub 180-4 via rotatable linkages 175-4 within ahousing 184-4. The motor assembly 160-4 is provided within the housing132-4 of the propulsion unit 130-4 and is mounted to a gimbaling base134-4 (e.g., a surface within the housing 132-4 comprising a gimbalingmechanism) within the housing 132-4. The motor assembly 160-4 includes aplurality of support bars 162-4 extending between a pair of supportplates 164-4 to define a frame, and a motor 165-4 coupled to a proximalend of a drive shaft 168-4. The motor 165-4 is configured to rotate theshaft 168-4 about an axis provided at a gimbal angle ϕ₄₋₁. A distal endof the shaft 168-4 is coupled to the variable pitch hub 180-4, which isprovided external to the housing 132-4 of the propulsion unit 130-4, viaa fastener 187-4. The rotation of the shaft 168-4 causes the propeller170-4 to rotate about the axis upon operation of the motor 165-4. Thepropulsion unit 130-4 further includes a plurality of plate supports150-4. Each of the plate supports 150-4 includes a shaft 152-4 that isjoined to a plate element 182-4 via ball joints (or other pivotableconnectors) 154-4 and to the gimbaling base 134-4 via knuckle joints (orother pivotable connectors) 156-4. Each of the plate supports 150-4further includes a linear actuator 155-4 that may extend or retract,independently or in concert, e.g., in response to one or morecomputer-generated control signals or instructions, to vary either anangle of the plate element 182-4 to which each is joined, a relativeposition of the plate element 182-4 with respect to the housing 184-4,or both the angle of the plate element 182-4 and the relative positionof the plate element 182-4 with respect to the housing 184-4.

As is shown in FIG. 1B and FIG. 1C, the plate supports 150-4 are mountedto the plate element 182-4 at three locations. Additionally, the plateelement 182-4 further includes a necked bore 185-4 through which theshaft 168-4 slidably extends. The necked bore 185-4 is alignedsubstantially perpendicular to a plane of the plate element 182-4, suchthat varying a planar angle of the plate element 182-4 causes an angleof the necked bore 185-4, substantially perpendicular to the plateelement 182-4, and the shaft 168-4, to vary accordingly. Therefore,operating the linear actuators 155-4 to extend or retract the platesupports 150-4 causes a corresponding location of the plate element182-4 to be raised or lowered within the housing 132-4, and at least oneof the planar angle of the plate element 182-4 or a relative distancebetween the plate element 182-4 and the housing 184-4 to be variedaccordingly.

As is also shown in FIG. 1B and FIG. 1C, the propeller 170-4 includesthree blades 172-4 that are mounted to the rotatable linkages 175-4within the housing 184-4 of the variable pitch hub 180-4, each at ablade pitch angle θ₄₋₁. The variable pitch hub 180-4 is rotatably joinedto the shaft 168-4 and enabled to rotate freely with respect to theplate element 182-4 about an axis defined by the shaft 168-4. Thevariable pitch hub 180-4 includes a ring bearing 177-4 provided betweenthe rotatable linkages 175-4 and the necked bore 185-4 within thehousing 184-4, enabling a relative distance between the housing 184-4and the plate element 182-4 to vary accordingly as the plate element182-4 moves with respect to the variable pitch hub 180-4. Where therotatable linkages 175-4 are configured to rotate the blades 172-4 basedon the relative distance between the housing 184 and the plate element184-4, changes in the relative distance that are caused by extensions orretractions of one or more of the linear actuators 155-4 may thus causechanges in the blade angles of the respective blades 172-4.

Moreover, the propulsion unit 130-4 may include one or more sets ofbearings coupled to the shaft 168-4 or other structural components. Forexample, as is shown in FIG. 1C, the ring bearing 177-4 is providedbetween the rotatable linkages 175-4 and the necked bore 185-4. A set ofbearings (not shown) may also be provided between the variable pitch hub180-4 and the plate element 182-4, to enable the variable pitch hub180-4 to freely rotate about the axis defined by the shaft 168-4 whilethe plate element 182-4 remains fixed in position. Other sets ofbearings (not shown) may be provided between the motor assembly 160-4and the shaft 168-4, or between the shaft 168-4 and the propeller 170-4,for example, to enable the shaft 168-4 to freely rotate while also beingsecured into place and aligned along a predefined axis.

The various components of the propellers of the present disclosure,including but not limited to the blades 172-4, may be formed from anysuitable materials that may be selected based on an amount of lift thatmay be desired in accordance with the present disclosure. In someimplementations, aspects of the propeller 170-4, e.g., the blades 172-4,may be formed from one or more plastics (e.g., thermosetting plasticssuch as epoxy or phenolic resins, polyurethanes or polyesters, as wellas polyethylenes, polypropylenes or polyvinyl chlorides), wood (e.g.,woods with sufficient strength properties such as ash), metals (e.g.,lightweight metals such as aluminum, or metals of heavier weightsincluding alloys of steel), composites or any other combinations ofmaterials. In some implementations, the aspects of the propeller 170-4may be formed of one or more lightweight materials including but notlimited to carbon fiber, graphite, machined aluminum, titanium orfiberglass.

As is shown in FIG. 1B and FIG. 1C, the motor 165-4 rotates the shaft168-4 and the propeller 170-4 at an angular velocity ω₄₋₁, therebygenerating a force F₄₋₁ in a direction of a gimbal angle ϕ₄₋₁ of thepropulsion unit 130-4, and causing sounds N₄₋₁ to radiate from thepropulsion unit 130-4, e.g., in one or more frequency spectrums. Thegimbal angle ϕ₄₋₁ of the propulsion unit 130-4 shown in FIG. 1B and FIG.1C is generally defined by an angle of the shaft 168-4, viz., zerodegrees, or vertically normal, with respect to the gimbaling base 134-4.

Each of the linear actuators 155-4 is configured to cause the platesupports 150-4 to independently recall or repulse a common operator,viz., the plate element 182-4, at each of the points to which the platesupports 150-4 are mounted, and to change the gimbal angle of thepropulsion unit 130-4 and/or the blade pitch angle of the blades 172-4accordingly. For example, where each of the linear actuators 155-4 isoperated in concert, and by a common extent (e.g., where each of theplate supports 150-4 extends or retracts by an equal amount,simultaneously or at different times), a change in a relative positionof the plate element 182-4 with respect to the housing 184-4 willresult, causing each of the blades 172-4 of the propeller 170-4 tochange accordingly. Where each of the linear actuators 155-4 is operatedindependently, and by a unique extent (e.g., where each of the platesupports 150-4 extends or retracts by a different amount, eithersimultaneously or at different times), changes in relative positions ofportions of the plate element 182-4 with respect to the housing 184-4will cause the gimbal angle of the propulsion unit 130-4, defined by theangle of the shaft 168-4 with respect to the housing 132-4, to vary by apositive amount with respect to normal. In some embodiments, a gimbalangle of the propulsion unit 130-4 may be varied within a range of zeroto fifteen degrees (0-15°) with respect to normal. The extent to whichthe gimbal angles may be varied is not limited, however.

Thus, because the shaft 168-4 slidably extends through the necked bore185-4, and because the motor assembly 160-4 is pivotably mounted to thegimbaling base 134-4, varying an angle of the plate element 182-4 usingthe linear actuators 155-4 causes an axis of the shaft 168-4 to vary,thereby modifying the gimbal angle of the propulsion unit 130-4.Moreover, in addition to extensions or retractions of the plate supports150-4, those of ordinary skill in the pertinent arts will recognize thatspeeds of the motor assembly 160-4 may also be modified accordingly. Insome other embodiments, shapes of the blades 172-4 may also be modifiedaccordingly.

As is discussed above, changes in blade pitch angles, gimbal angles,motor speeds and/or blade shapes of one or more propulsion units of anaerial vehicle may also result in changes to the forces generated bysuch propulsion units, or the overall net force provided to the aerialvehicle by such propulsion units. Therefore, where a change in position,velocity or acceleration of an aerial vehicle is desired, pitch angles,gimbal angles, motor speeds or blade shapes may be adjusted accordingly,in order to vary the a force (e.g., lift and/or thrust) supplied to theaerial vehicle by one or more of such propulsion units, and effect thedesired change in position, velocity and/or acceleration accordingly.

Referring to FIG. 1D and FIG. 1E, the aerial vehicle 110 is shown asfree body diagrams with respect to a current net force vector and adesired net force vector. For example, referring to FIG. 1D, where theaerial vehicle 110 is to hover, a magnitude of the net force F_(NET-1)provided by the operation of the propulsion units 130-1, 130-2, 130-3,130-4 must equal a magnitude of the weight w₁₁₀ of the aerial vehicle110, in an opposite direction, excluding the effects of wind forces orother lateral effects, such that a velocity v₁ of the aerial vehicle 110is zero, in order to cause the aerial vehicle 110 to hover. Where achange in position, velocity and/or acceleration is desired, however,the net force provided by the operation of the propulsion units 130-1,130-2, 130-3, 130-4 must change accordingly. For example, referring toFIG. 1E, in order cause the aerial vehicle 110 to transition from ahovering state at a velocity v₁ of zero to a non-zero velocity v₂, thepropulsion units 130-1, 130-2, 130-3, 130-4 may be reconfigured togenerate a net force F_(NET-2), such as by changing a motor speed, ablade pitch angle, a gimbal angle and/or a blade shape of one or more ofthe propulsion units 130-1, 130-2, 130-3, 130-4.

Referring to FIG. 1F, the propulsion unit 130-4 is shown as generatingforce having a vector F₄₋₂, and radiating sounds N₄₋₂ in one or morefrequency spectrums, based on an angular velocity ω₄₋₂ of the motorassembly 160-4 and the propeller 170-4, a gimbal angle ϕ₄₋₂ of thepropulsion unit 130-4 and a blade pitch angle θ₄₋₂ of the blades 172-4of the propeller 170-4. The force vector F₄₋₂ may be achieved by theoperation of the linear actuators 155-4 and/or one or more elements ofthe propulsion unit 130-4, e.g., to change the speed of the motorassembly 160-4, the blade pitch angles θ₄₋₂ of the blades 172-4 of thepropeller 170-4, the gimbal angle ϕ₄₋₂ of the propulsion unit 130-4and/or a shape of one or more of the blades 174-2. For example, as isshown in FIG. 1F, and as compared to the configuration of the propulsionunit 130-4 shown in FIG. 1B or FIG. 1C, two of the linear actuators155-4 have been extended in order to elevate at least a first portion ofthe plate element 182-4, and one of the linear actuators 155-4 has beenretracted in order to lower at least a second portion of the plateelement 182-4. The operation of the linear actuators 155-4 thus causesthe gimbal angle ϕ_(4E) of the propulsion unit 130-4, defined on anangle of the shaft 168-4, to change. Therefore, forces generated by thepropeller 170-4 during operation are supplied along an axiscorresponding to the gimbal angle ϕ₄₋₂, and regions to which noisesradiated from the propulsion unit 130-4 are directed during operationmay vary accordingly. Likewise, the operation of the linear actuators155-4 also places each of the blades 172-4 of the propeller 170-4 at ablade pitch angle θ₄₋₂, e.g., by changing the relative position of thevariable pitch hub 180-4 with respect to the plate element 182-4.

Alternatively, those of ordinary skill in the pertinent art willrecognize that a force having a vector (e.g., a magnitude and direction)may be maintained at a constant level even after one or more of a motorspeed, a blade pitch angle, a gimbal angle and/or shapes of propellerblades is modified. For example, because variables such as motor speeds,blade pitch angles, gimbal angles and/or blade shapes each contribute tothe forces (e.g., lift and/or thrust) generated by a propeller and/orpropulsion unit in operation, a change in one of the variables (e.g., anincrease or decrease in motor speed) may be counteracted by a change inone or more of the other variables (e.g., a decrease or increase in oneor more blade pitch angles, gimbal angles or blade shapes) in order tomaintain a magnitude or a direction of force provided by the propelleror propulsion unit. Likewise, each of the variables makes an independentcontribution to a level of sound or noise radiated by the propellerand/or propulsion unit during operation. Thus, by controlling thevariables associated with the operation of a propeller or propulsionunit, a given force may be maintained but with different effects onsound or noise radiated in an environment in which the aerial vehicle isoperating, and such variables may be selected with regard to specificgoals or objectives such as maneuverability, fuel efficiency and/orbattery life, or adverse weather conditions while responding to demandsfor the force.

Accordingly, an aerial vehicle, such as the aerial vehicle 110 of FIGS.1A through 1F, may be equipped with one or more propulsion units havingmotors and propellers that may be configured to operate in one or moredistinct modes, which may be selected on any basis. For example, one ormore modes of operation may be selected based on a position or locationof the aerial vehicle, or any operational characteristics orenvironmental conditions that may be encountered by the aerial vehicleduring flight. In particular, a propulsion unit of the presentdisclosure may include common operators that are configured to vary bothblade pitch angles and/or gimbal angles, e.g., using one or more linearactuators or other components that may extend or retract, as needed, andalso one or more components for varying motor speeds and/or bladeshapes. Thus, a propulsion unit may be configured to not only vary botha magnitude and direction of a given force provided thereby, but alsoprovide that same magnitude and direction of the force in any number ofconfigurations of blade pitch angles, gimbal angles, motor speeds and/orblade shapes, in order to shape, control or manipulate a sound pressurelevel and/or frequency spectrums of sounds that are generated by thepropulsion unit individually, or the aerial vehicle as a whole, duringoperation.

Referring to FIG. 2, a block diagram of components of one system 200 foroperating an aerial vehicle having one or more embodiments of propulsionunits in accordance with embodiments of the present disclosure is shown.The system 200 of FIG. 2 includes an aerial vehicle 210 and a dataprocessing system 280 connected to one another over a network 290.

The aerial vehicle 210 includes a processor 212, a memory 214 and atransceiver 216. The aerial vehicle 210 further includes a plurality ofenvironmental or operational sensors 220, a plurality of sound sensors225. The aerial vehicle 210 also includes a propulsion unit 230 havingone or more blade controllers 240, one or more linear actuators 255-1,255-2, 255-3, a motor 260 and a propeller 270 that is physically coupledto the motor 260 and in communication with the one or more bladecontrollers 240.

The processor 212 may be configured to perform any type or form ofcomputing function associated with any operation of the aerial vehicle210, including but not limited to the execution of one or more machinelearning algorithms or techniques, e.g., for predicting one or moreattributes of the aerial vehicle 210 based on historical data regardingprior operations of the aerial vehicle 210, or one or more other aerialvehicles, or for processing acoustic data captured during the operationof the aerial vehicle 210, e.g., by the sound sensors 225. The processor212 may control any aspects of the operation of the aerial vehicle 210and the one or more computer-based components thereon, including but notlimited to the transceiver 216, the environmental or operational sensors220 or the sound sensors 225. The aerial vehicle 210 may likewiseinclude one or more control systems (not shown) that may generateinstructions for operating any number of components of the aerialvehicle 210, e.g., the blade controllers 240, the linear actuators255-1, 255-2, 255-3, the motor 260 and/or the propeller 270, as well asany rudders, ailerons, flaps or other control surfaces (not shown)provided thereon. Such control systems may be associated with one ormore other computing devices or machines, and may communicate with thedata processing system 280 or one or more other computer devices (notshown) over the network 290, as indicated by line 218, through thesending and receiving of digital data. For example, the processor 212may be operate or be associated with one or more electronic speedcontrols, feedback circuits or other components for controlling theoperation of the blade controllers 240, the linear actuators 255-1,255-2, 255-3, the motor 260 and/or the propeller 270, or any controlsurfaces provided thereon.

The aerial vehicle 210 further includes one or more memory or storagecomponents 214 for storing any type of information or data, e.g.,instructions for operating the aerial vehicle 210, the propulsion unit230, the blade controllers 240, the linear actuators 255-1, 255-2,255-3, the motor 260 or the propeller 270, as well as information ordata captured by one or more of the environmental or operational sensors220 or the sound sensors 225.

The transceiver 216 may be configured to enable the aerial vehicle 210to communicate through one or more wired or wireless means, e.g., wiredtechnologies such as Universal Serial Bus (or “USB”) or fiber opticcable, or standard wireless protocols such as Bluetooth® or any WirelessFidelity (or “WiFi”) protocol, such as over the network 290 or directly.

The operational sensors 220 may include any components or features fordetermining one or more attributes of an environment in which the aerialvehicle 210 is operating or may be expected to operate, or one or moreoperational characteristics of the aerial vehicle 210, includingextrinsic information or data or intrinsic information or data. Forexample, the operational sensors 220 may include, but are not limitedto, any types of receivers or sensors. For example, one such sensor maybe a Global Positioning System (“GPS”) sensor, or any device, component,system or instrument adapted to receive signals (e.g., trilaterationdata or information) relating to a position of the aerial vehicle 210from one or more GPS satellites of a GPS network (not shown). Anothersuch sensor may be a compass, or any device, component, system, orinstrument adapted to determine one or more directions with respect to aframe of reference that is fixed with respect to the surface of theEarth (e.g., a pole thereof). The operational sensors 220 may furtherinclude a speedometer or any device, component, system, or instrumentfor determining a speed or velocity of the aerial vehicle 210, and mayinclude related components (not shown) such as pitot tubes,accelerometers, or other features for determining speeds, velocities, oraccelerations.

Likewise, the operational sensors 220 may include any device, component,system, or instrument for determining an altitude of the aerial vehicle210, and may include any number of barometers, transmitters, receivers,range finders (e.g., laser or radar) or other features. The operationalsensors 220 may further include thermometers, barometers or hygrometers,or any devices, components, systems, or instruments for determininglocal air temperatures, atmospheric pressures, or humidities,respectively, within a vicinity of the aerial vehicle 210. Theoperational sensors 220 also include one or more gyroscopes, or anymechanical or electrical device, component, system, or instrument fordetermining an orientation, e.g., the orientation of the propulsion unit230 or the aerial vehicle 210, or of one or more components thereof. Insome embodiments, the operational sensors 220 may include a traditionalmechanical gyroscope having at least a pair of gimbals and a flywheel orrotor, or an electrical gyroscope such as a dynamically tuned gyroscope,a fiber optic gyroscope, a hemispherical resonator gyroscope, a Londonmoment gyroscope, a microelectromechanical sensor gyroscope, a ringlaser gyroscope, or a vibrating structure gyroscope, or any other typeor form of electrical component for determining an orientation of theaerial vehicle 210 or one or more components thereof.

Those of ordinary skill in the pertinent arts will recognize that theoperational sensors 220 may further include any type or form of deviceor component for determining an environmental condition within avicinity of the aerial vehicle 210, or an operational characteristic ofthe aerial vehicle 210, in accordance with the present disclosure. Forexample, the operational sensors 220 may include one or more airmonitoring sensors (e.g., oxygen, ozone, hydrogen, carbon monoxide orcarbon dioxide sensors), infrared sensors, ozone monitors, pH sensors,magnetic anomaly detectors, metal detectors, radiation sensors (e.g.,Geiger counters, neutron detectors, alpha detectors), attitudeindicators, depth gauges, accelerometers, tachometers or the like, aswell as one or more imaging devices (e.g., digital cameras).

The sound sensors 225 may include other components or features fordetecting and capturing sound energy in a vicinity of an environment inwhich the aerial vehicle 210 is operating, or may be expected tooperate, including but not limited to one or more microphones,piezoelectric sensors or vibration sensors. For example, suchmicrophones may be any type or form of transducer (e.g., a dynamicmicrophone, a condenser microphone, a ribbon microphone, a crystalmicrophone) configured to convert acoustic energy of any intensity andacross any or all frequencies into one or more electrical signals, andmay include any number of diaphragms, magnets, coils, plates, or otherlike features for detecting and recording such energy. Such microphonesalso be provided as a discrete component, or in combination with one ormore other components, e.g., an imaging device such as a digital camera.Furthermore, such microphones may be configured to detect and recordacoustic energy from any and all directions.

Likewise, such piezoelectric sensors may be configured to convertchanges in pressure, including but not limited to such pressure changesthat are initiated by the presence of acoustic energy across variousbands of frequencies, to electrical signals, and may include one or morecrystals, electrodes or other features. Such vibration sensors may beany device configured to detect vibrations of one or more components ofthe aerial vehicle 210, and may also be a piezoelectric device. Forexample, a vibration sensor may include one or more accelerometers,e.g., an application-specific integrated circuit and one or moremicroelectromechanical sensors in a land grid array package, that areconfigured to sense differential accelerations along one or more axesover predetermined periods of time and to associate such accelerationswith levels of vibration and, therefore, sound.

As is noted above, the propulsion unit 230 includes the bladecontrollers 240, the linear actuators 255-1, 255-2, 255-3, the motor 260and the propeller 270. The blade controllers 240 may include a pluralityof components for operating and/or adjusting one or more attributes ofblades of the propeller 270 at a predetermined time or in accordancewith a predefined schedule, or in response to one or more controlsignals, sensed environmental conditions or sensed operationalcharacteristics. For example, such controllers 240 may be configured torotate blade tips of such blades, change the shapes of such blades, ormodify any number of other attributes of such blades. The bladecontrollers 240 may thus control, initiate or operate one or moremechanical or electrical features provided on or in association with thepropeller 270 for the purpose of altering one or more attributesthereof. The linear actuators 255-1, 255-2, 255-3 may be configured toextend or retract in a straight line, e.g., in response to one or morecontrol signals or commands, thereby increasing or decreasing a distancebetween two components of the propulsion unit 230 to which each of thelinear actuators 255-1, 255-2, 255-3 is joined, such as the gimbalingbase 134-4 and the plate element 182-4 shown in FIG. 1B, 1C or 1F. Forexample, the linear actuators 255-1, 255-2, 255-3 may include one ormore screws or other threaded elements having operators configured forrotary motion about such elements, as well as one or more hydraulic,pneumatic or electromechanical operators. Any component for causinglinear motion between two points within the propulsion unit 230 may beincluded as one or more of the linear actuators 255-1, 255-2, 255-3 ofthe present disclosure.

The data processing system 280 includes one or more physical computerservers 282 having a plurality of databases 284 associated therewith, aswell as one or more computer processors 286 provided for any specific orgeneral purpose. For example, the data processing system 280 of FIG. 2may be independently provided for the exclusive purpose of receiving,analyzing or storing information or data regarding one or more missionsor evolutions that have been performed or are scheduled to be performedby the aerial vehicle 210, including but not limited to information ordata regarding demands for force (e.g., lift and/or thrust) during suchmissions or evolutions, or sounds or noises that have been emitted orare expected to be emitted during such missions or evolutions.Alternatively, the data processing system 280 may be provided inconnection with one or more physical or virtual services configured toreceive, analyze or store instructions for operating the aerial vehicle210 or other information or data, as well as to perform one or moreother functions. The servers 282 may be connected to or otherwisecommunicate with the databases 284 and the processors 286. The databases284 may store any type of information or data, including but not limitedto information or data regarding the operation of the aerial vehicle210, e.g., information or data captured by one or more of theoperational sensors 220 or the sound sensors 225, as well as informationor data regarding operation of the blade controllers 240, the linearactuators 255-1, 255-2, 255-3, the motor 260 or the propeller 270, whichmay be correlated or otherwise associated with the information or datacaptured by one or more of the operational sensors 220 or the soundsensors 225.

The servers 282 and/or the computer processors 286 may also connect toor otherwise communicate with the network 290, as indicated by line 288,through the sending and receiving of digital data. For example, the dataprocessing system 280 may include any facilities, stations or locationshaving the ability or capacity to receive and store information or data,such as media files, in one or more data stores, e.g., media filesreceived from the aerial vehicle 210, or from one another, or from oneor more other external computer systems (not shown) via the network 290.In some embodiments, the data processing system 280 may be provided in aphysical location. In other such embodiments, the data processing system280 may be provided in one or more alternate or virtual locations, e.g.,in a “cloud”-based environment. In still other embodiments, the dataprocessing system 280 may be provided onboard one or more aerialvehicles, including but not limited to the aerial vehicle 210.

The network 290 may be any wired network, wireless network, orcombination thereof, and may comprise the Internet in whole or in part.In addition, the network 290 may be a personal area network, local areanetwork, wide area network, cable network, satellite network, cellulartelephone network, or combination thereof. The network 290 may also be apublicly accessible network of linked networks, possibly operated byvarious distinct parties, such as the Internet. In some embodiments, thenetwork 290 may be a private or semi-private network, such as acorporate or university intranet. The network 290 may include one ormore wireless networks, such as a Global System for MobileCommunications (GSM) network, a Code Division Multiple Access (CDMA)network, a Long Term Evolution (LTE) network, or some other type ofwireless network. Protocols and components for communicating via thenetwork 290 and/or the Internet or any of the other aforementioned typesof communication networks are well known to those skilled in the art ofcomputer communications and thus, need not be described in more detailherein.

The computers, servers, devices and the like described herein have thenecessary electronics, software, memory, storage, databases, firmware,logic/state machines, microprocessors, communication links, displays orother visual or audio user interfaces, printing devices, and any otherinput/output interfaces to provide any of the functions or servicesdescribed herein and/or achieve the results described herein. Also,those of ordinary skill in the pertinent art will recognize that usersof such computers, servers, devices and the like may operate a keyboard,keypad, mouse, stylus, touch screen, or other device (not shown) ormethod to interact with the computers, servers, devices and the like, orto “select” an item, link, node, hub or any other aspect of the presentdisclosure.

The aerial vehicle 210 or the data processing system 280 may use anyweb-enabled or Internet applications or features, or any otherclient-server applications or features including E-mail or othermessaging techniques, to connect to the network 290, or to communicatewith one another, such as through short or multimedia messaging service(SMS or MMS) text messages. For example, the aerial vehicle 210 may beadapted to transmit information or data in the form of synchronous orasynchronous messages to the data processing system 280 or to any othercomputer device in real time or in near-real time, or in one or moreoffline processes, via the network 290. Those of ordinary skill in thepertinent art would recognize that the aerial vehicle 210 or the dataprocessing system 280 may communicate with any of a number of computingdevices that are capable of communicating over the network 290,including but not limited to set-top boxes, personal digital assistants,digital media players, web pads, laptop computers, desktop computers,electronic book readers, and the like. The protocols and components forproviding communication between such devices are well known to thoseskilled in the art of computer communications and need not be describedin more detail herein.

The data and/or computer-executable instructions, programs, firmware,software and the like (also referred to herein as “computer-executable”components) described herein may be stored on a computer-readable mediumthat is within or accessible by computers or computer components such asthe processor 212 or the processor 284, or any other computers orcontrol systems utilized by the aerial vehicle 210 or the dataprocessing system 280, and having sequences of instructions which, whenexecuted by a processor (e.g., a central processing unit, or “CPU”),cause the processor to perform all or a portion of the functions,services and/or methods described herein. Such computer-executableinstructions, programs, software, and the like may be loaded into thememory of one or more computers using a drive mechanism associated withthe computer readable medium, such as a floppy drive, CD-ROM drive,DVD-ROM drive, network interface, or the like, or via externalconnections.

Some embodiments of the systems and methods of the present disclosuremay also be provided as a computer-executable program product includinga non-transitory machine-readable storage medium having stored thereoninstructions (in compressed or uncompressed form) that may be used toprogram a computer (or other electronic device) to perform processes ormethods described herein. The machine-readable storage media of thepresent disclosure may include, but is not limited to, hard drives,floppy diskettes, optical disks, CD-ROMs, DVDs, ROMs, RAMs, erasableprogrammable ROMs (“EPROM”), electrically erasable programmable ROMs(“EEPROM”), flash memory, magnetic or optical cards, solid-state memorydevices, or other types of media/machine-readable medium that may besuitable for storing electronic instructions. Further, embodiments mayalso be provided as a computer-executable program product that includesa transitory machine-readable signal (in compressed or uncompressedform). Examples of machine-readable signals, whether modulated using acarrier or not, may include, but are not limited to, signals that acomputer system or machine hosting or running a computer program can beconfigured to access, or including signals that may be downloadedthrough the Internet or other networks.

One or more of the propulsion units of the present disclosure may beconfigured to generate a selected force based on a plurality ofvariables associated with the motors or propellers provided thereon. Forexample, as is discussed above, a vector associated with a forcegenerated by a propulsion unit (e.g., a magnitude of the force, and adirection of the force) may be selected based at least in part on one ormore of a motor speed, a gimbal angle, a blade pitch angle and/or ablade shape, each of which may be modified during or prior to operationof the propulsion unit. Referring to FIG. 3, a portion of one embodimentof an aerial vehicle 310 of the present disclosure is shown. Exceptwhere otherwise noted, reference numerals preceded by the number “3”shown in FIG. 3 indicate components or features that are similar tocomponents or features having reference numerals preceded by the number“2” shown in FIG. 2 or by the number “1” shown in FIGS. 1A through 1F.

As is shown in FIG. 3, the portion of the aerial vehicle 310 includes apropulsion unit 330 having a plurality of adjustable plate supports 350,a motor 360 and a propeller 370. The motor 360 is provided within ahousing of the propulsion unit 330, and is coupled to the propeller 370via a drive shaft. The propeller 370 is provided external to the housingof the propulsion unit 330 in which the motor 360 is provided, andincludes a plurality of blades, each of which is coupled to a variablepitch hub 380, e.g., by a rotatable linkage (not shown). The threeadjustable plate supports 350 are joined to a plate element 382 at threepoints and may extend or retract, as needed, to vary either a planarangle of the plate element 382 and, therefore, a gimbal angle of thepropulsion unit 330, or pitch angles of the blades of the propeller 370,or both the gimbal angle of the propulsion unit 330 and the pitch anglesof the blades of the propeller 370.

In accordance with the present disclosure, a force F is generated by thepropulsion unit 330 based on a number of factors, many of which may beautomatically and/or selectively chosen and/or varied in accordance withthe present disclosure. For example, a magnitude and a direction of theforce F may depend on an angular velocity ω of the motor 360 and/orpropeller 370, which is defined based on an operating speed of the motor360. Additionally, the magnitude and/or the direction of the force F mayalso depend on a gimbal angle ϕ of the propulsion unit 330, which isdefined based at least in part on an angular orientation of an axis ofthe shaft 365 about which the propeller 370 rotates, and which mayitself be defined based on an angular orientation of the plate element382. The magnitude and/or the direction of the force F may furtherdepend on pitch angles θ of the blades of the propeller 370, which maybe defined based on a relative distance between the variable pitch hub380 and the plate element 382. The magnitude and/or the direction of theforce F may also depend on shapes and/or dimensions of the blades of thepropeller 370, e.g., dimensions of the faces or backs of such blades,such as a length l or a width w of the blades, as well as shapes orcontours of leading edges, trailing edges, or any appurtenancesextending from the blades. In some embodiments, the magnitude and/ordirection of the force F may depend on whether the propeller 370 isbalanced or imbalanced.

Forces generated by propulsion units, such as the force F generated bythe propulsion unit 330, may be represented in a vector having one ormore components or aspects in three-dimensional space. As is shown inFIG. 3, the force F may be represented in spherical coordinates, with X,Y and Z components along respective axes or dimensions and with thegimbal angle ϕ from normal. Thus, the length of the vector correspondingto the force F is proportional to its magnitude, and the angle ϕ of thevector corresponding to the force is associated with its direction. Thevarious X, Y and Z components are indicative of magnitudes of forcealong each of the axes or in each of the three dimensions. Where anaerial vehicle, such as the aerial vehicle 110 of FIGS. 1A through 1F,includes one or more propulsion units, the effects of the forcesgenerated by each of the propulsion units result in a net force that isapplied to the aerial vehicle. For example, a magnitude of a net forcesupplied to the aerial vehicle having multiple propulsion units of thepresent disclosure may be determined based on a sum of the forcesgenerated by such propulsion units in each of the X, the Y or the Zdirections, and a direction of the net force may be determined based thesums of such forces, and according to the Pythagorean theorem.

Therefore, because each of the forces generated by each of thepropulsion units provided on an aerial vehicle in accordance with thepresent disclosure is determined as function of the angular velocities(or speeds) of the respective motors, the gimbal angles of thepropulsion units, or the pitch angles and shapes or dimensions of thepropeller blades of such propulsion units, an aerial vehicle may achievea desired net force by controlling the motors, the gimbal angles, thepitch angles and the shapes of the blades of each of the respectivepropulsion units. Moreover, in some embodiments, the gimbal angles andthe blade pitch angles may be specifically selected and controlled usingone or more linear actuators, such as those that may be provided withinor in association with the adjustable plate supports 350 of FIG. 3. Inthis regard, because a motor speed, a gimbal angle, a blade pitch angleand a blade shape may contribute to the sounds generated by a propulsionunit during operation in different ways, the manner in which a givenforce is generated by a propulsion unit may be altered to vary thesounds that are also generated by the propulsion unit during operation.

As is discussed above, blades may be joined to propeller in any mannerthat enables the pitch angles of such blades to be manipulated duringoperation by one or more common elements, such as the plate element182-4 and the linear actuators 155-4 shown in FIG. 1B, 1C or 1F, inaccordance with the present disclosure. Referring to FIGS. 4A through4F, views of aspects of one embodiment of an aerial vehicle inaccordance with embodiments of the present disclosure are shown. Exceptwhere otherwise noted, reference numerals preceded by the number “4”shown in FIGS. 4A through 4F indicate components or features that aresimilar to components or features having reference numerals preceded bythe number “3” shown in FIG. 3, by the number “2” shown in FIG. 2 or bythe number “1” shown in FIGS. 1A through 1F.

FIG. 4A shows an exploded view of portions of a plurality of platesupports 450, a propeller 470 and a variable pitch hub 480. FIG. 4Bshows a view of the portions of the plate supports 450, the propeller470 and the variable pitch hub 480 of FIG. 4A in an assembled fashion.FIG. 4C shows a sectional view of the portions of the plate supports450, the propeller 470 and the variable pitch hub 480 of FIG. 4A in theassembled fashion. As is shown in FIGS. 4A, 4B and 4C, each of the platesupports 450 includes a shaft 452, a pivotable connector 454 (e.g., aball-and-socket connector) and a linear actuator 455, and is joined toone corner of a triangle-shaped plate element 482 by the pivotableconnector 454. Each of the plate supports 450 may also be mounted to abase or other surface within a housing (not shown). Each of the linearactuators 455 may be configured to change the lengths of the respectiveplate supports 450, thereby elevating or lowering a respective corner ofthe plate element 482, and changing an angle of a plane of the plateelement 482 and/or an angle of a pitch of one or more of the blades 472accordingly.

As is also shown in FIGS. 4A, 4B and 4C, the propeller 470 includes aplurality of blades 472 joined to a housing 484 of the variable pitchhub 480. Each of the blades 472 includes a pivotable root 474 that maybe inserted into a variable pitch mechanism 475 provided within thehousing 484 of the variable pitch hub 480. In some embodiments, thevariable pitch mechanisms 475 are configured to pivot the blades 472 bytheir respective roots 474 to predetermined extents in response torelative movements between the plate element 482 and the housing 484.

As is also shown in FIGS. 4A, 4B and 4C, a shaft 468 slidably extendsthrough a necked bore 485 in the plate element 482 and is joined to thevariable pitch hub 480 by a fastener 487 (e.g., a bolt, a screw, a clip,a cotter pin, a rivet, or any other type or form of fastener by whichthe shaft 468 may be joined to the variable pitch hub 480). Because thenecked bore 485 is substantially perpendicular to the plate element 482,the plate element 482 may move in a relative manner along the shaft 468in order to vary a distance of the plate element 482 with respect to thehousing 484 of the variable pitch hub 480, thereby causing the variablepitch mechanisms 475 to pivot the blades 472 by their respective roots474 accordingly.

Thus, when a relative position of the plate element 482 changes withrespect to the variable pitch hub 480, e.g., by extending or retractingone or more plate supports 450 coupled to the plate element 482, each ofthe blades 472 is caused to rotate about the axis defined by thepivotable root 474, varying a pitch angle of the blades 472 thereby. Forexample, as is shown in FIG. 4C, when the variable pitch hub 480 is at afirst height Δh_(D) with respect to the plate element 482, the blades472 are caused to pivot about axes defined by their respective roots474, thereby imparting a positive pitch angle OD to the blades 472 in anamount proportional to the first height Δh_(D) of the variable pitch hub480 with respect to the plate element 482.

As is shown in FIG. 4E, when the variable pitch hub 480 is at a secondheight Δh_(E) with respect to the plate element 482, the blades 472 areprovided at a second pitch angle θ_(E), e.g., a neutral pitch angle, orwhere θ_(E)=0°. As is shown in FIG. 4F, when the variable pitch hub 480is at a third height Δh_(F) with respect to the plate element 482, theblades 472 are provided at a third pitch angle θ_(F), e.g., a negativepitch angle θ_(F) is imparted to the blades 472 in an amountproportional to the third height Δh_(F) of the variable pitch hub 480with respect to the plate element 482.

As is discussed above, in accordance with the present disclosure, apitch angle of a propeller's blades may be varied, and a gimbal angle ofthe propeller may be defined, using a common element that may bemanipulated using one or more linear actuators or like components. Insome embodiments, changing a relative position and/or orientation ofsuch an element may vary either the pitch angle of the blades, such asis discussed above with regard to FIGS. 4D through 4F, or the gimbalangle of the propeller, or may vary both the pitch angle of the bladesand the gimbal angle of the propeller.

Referring to FIGS. 5A through 5D, views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the present disclosureare shown. Except where otherwise noted, reference numerals preceded bythe number “5” shown in FIGS. 5A through 5D indicate components orfeatures that are similar to components or features having referencenumerals preceded by the number “4” shown in FIGS. 4A through 4F, by thenumber “3” shown in FIG. 3, by the number “2” shown in FIG. 2 or by thenumber “1” shown in FIGS. 1A through 1F.

As is shown in FIG. 5A, a plate element 582 having a necked bore 585extending substantially perpendicularly therethrough is coupled to aplurality of plate supports 550-1, 550-2, 550-3. Each of the platesupports 550-1, 550-2, 550-3 includes a shaft 552-1, 552-2, 552-3, apivotable connector 554-1, 554-2, 554-3 and a linear actuator 555-1,555-2, 555-3 that is configured to extend or retract in order to vary aposition and/or orientation of the plate element 582. Where the plateelement 582 is associated with rotating components of a propeller (notshown), such as the variable pitch hub 480 of FIGS. 4A through 4F,changing a relative position of the plate element 582 using the platesupports 550-1, 550-2, 550-3 may change pitch angles of blades mountedto the propeller, while changing an angle of orientation of the plateelement 582 using the plate supports 550-1, 550-2, 550-3 may change agimbal angle of the propeller. Thus, the plate supports 550-1, 550-2,550-3 may be used to vary both a magnitude of a force generated by apropeller, and a direction of the force generated by the propeller,accordingly.

For example, as is shown in FIG. 5B, blade pitch angles may be changedby moving each of the linear actuators 555-1, 555-2, 555-3 in concert,and by equal amounts and in a common direction, thereby raising orlowering a relative position of a corresponding portion of the plateelement 582 and maintaining a gimbal angle ϕ₁ of a propeller providedthereon (not shown) at approximately zero degrees, or normal. Where adirection of the force generated by a propeller, which is defined by agimbal angle of the propeller, is to be varied, the linear actuators555-1, 555-2, 555-3 may be operate separately and by different amountsand/or in different directions to vary an angular orientation of theplate element 580. As is shown in FIGS. 5C and 5D, extending orretracting the linear actuators 555-1, 555-2, 555-3 to different extentsimparts positive gimbal angles ϕ₂, ϕ₃ to a propeller provided thereon(not shown), thereby varying a direction of the forces (e.g., liftand/or thrust) generated by the propeller in a manner consistent withthe variations of the gimbal angles ϕ₂, ϕ₃.

Accordingly, where a force in a predetermined magnitude and/or directionis demanded from a propulsion unit, a magnitude of the force may bedefined by adjusting a pitch angle of the blades of a propeller, and adirection of the force may be defined by adjusting a gimbal angle of thepropulsion unit or propeller, using a common system such as a plateelement that is coupled to a plurality of linear actuators and providedin association with a variable pitch hub. The linear actuators may beconfigured to adjust the pitch angle of the blades of the propeller byextending or retracting by a common extent and substantiallysimultaneously. The linear actuators may also be configured to adjustthe gimbal angle of the propulsion unit or propeller by extending orretracting to different extents or at different times. In someembodiments, three linear actuators may be coupled to a plate element orlike feature associated with a motor and/or a propeller, consistent withthe geometric lemma that any plane may be defined by three points inspace. A plane of the plate element may therefore be selected byadjusting the positions of the three points at which the linearactuators are joined to the plate element. In other embodiments, morethan three linear actuators may be provided to adjust an angle of aplate element. In still other embodiments, fewer than three linearactuators may be provided. Moreover, those of ordinary skill in thepertinent arts will recognize that a plate element may be manipulatedusing one or more linear actuators provided about a perimeter of theplate element, such as is shown in FIGS. 5A through 5D, or elsewhere onthe plate element, in accordance with the present disclosure.

As is discussed above, and as will be recognized by those of ordinaryskill in the pertinent arts in view of the present disclosure, a levelof force generated by a propeller may be varied in any number of otherways. For example, an angular velocity or speed of a motor coupled tothe propeller may be increased or decreased, and the force generated bythe rotating propeller may increase or decrease by a correspondingextent, e.g., as a function of a square of the angular velocity orspeed. Likewise, in addition to blade pitch, one or more additionalaspects of the blades and their physical construction may be variedaccordingly.

Referring to FIGS. 6A and 6B, views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the present disclosureare shown. Except where otherwise noted, reference numerals preceded bythe number “6” shown in FIGS. 6A and 6B indicate components or featuresthat are similar to components or features having reference numeralspreceded by the number “5” shown in FIGS. 5A through 5D, by the number“4” shown in FIGS. 4A through 4F, by the number “3” shown in FIG. 3, bythe number “2” shown in FIG. 2 or by the number “1” shown in FIGS. 1Athrough 1F.

As is shown in FIGS. 6A and 6B, a propulsion unit 615 includes apropeller 670 having a pair of blade roots 672, with each of the bladeroots 672 being joined to a hub 680 at a proximal end and a blade tip674 that may be retracted or otherwise varied with respect to the bladeroots 672 at a distal end. The propulsion unit 615 may further include anumber of additional components within a housing thereof, including oneor more motors, drive shafts, bearings, linear actuators, controllers orother components for causing the propeller 670 to rotate at a desiredangular velocity, for aligning the propeller 670 at a desired gimbalangle and/or for changing a pitch angle of one or more of the blades672, including but not limited to one or more of the components shown inFIGS. 3, 4A through 4F or 5A through 5D, or like components.

The blade tips 674 may be configured to rotate about a tangential axisdefined by a hinged connection with respect to a radial axis defined bythe blade root 672. As is further shown in FIG. 6A, each of the bladetips 674 is aligned along radial axes defined by a respective one of theblade roots 672. Each of the blade tips 674 and each of the blade roots672 defines an airfoil shape for generating lift when the propeller 670is rotated about an axis defined by the hub 680, and may, in someembodiments, include rounded leading edges and pointed trailing edgesthat may include upper surfaces or lower surfaces having symmetrical orasymmetrical shapes or cross-sectional areas. The airfoil shapes definedby the blade roots 672 and the blade roots 674, and the pitch angles atwhich the blade roots 672 are mounted to the hub 680, may be selectedbased on an amount of lift and/or thrust desired to be provided by thepropeller 670. Moreover, the propeller 670 may be configured to rotatethe blade tips 674 with respect to axes defined by the blade roots 672,either statically or dynamically during operation. As is shown in FIG.6A, the blade tips 674 are rotated vertically upwardly with respect tothe blade roots 672 by adjustable cant angles that may be limited onlyby constraints resulting from the construction of the propeller 670.

For example, the blade tips 674 may be rotated with respect to the bladeroots 672, at any time or in accordance with a predetermined schedule(e.g., based at least in part on a transit plan involving travel from anorigin to a destination, and optionally through one or more interveningwaypoints), or in response to a sensed operating characteristic (e.g.,dynamic attributes such as altitudes, courses, speeds, rates of climb ordescent, turn rates, accelerations, tracked positions, fuel level,battery level or radiated noise; or physical attributes such asdimensions of structures or frames, numbers of propellers or motors,operating speeds of such motors) or environmental condition (e.g.,temperatures, pressures, humidities, wind speeds, wind directions, timesof day or days of a week, month or year when an aerial vehicle isoperating, measures of cloud coverage, sunshine, or surface conditionsor textures).

Additionally, the blade tips 674 may be rotated with respect to theblade roots 672 in any manner or by any means with respect toorientations or configurations defined by the blade roots 672, and toany extent. For example, one or more of the blade roots 672 may includeone or more mechanical operators within airfoils of the blade roots 672that are configured to cause the blade tips 674 to be positioned at aselected cant angle with respect to the blade roots 672. For example, insome embodiments, the propeller 670 may include a gear and cam assemblythat rotates based on the rotation of a drive shaft (not shown), andcauses a follower or push rod to cause the blade tip 674 to be rotatedabout a hinged connection to a different cant angle accordingly. In someother embodiments, the propeller 670 may include a cable-driven tensionassembly that causes a cable connected to one or more of the blade tips674 to extend or retract against centrifugal forces acting on the bladetips 674, as necessary, in order to cause the blade tip 674 to rotateabout a hinge to a different cant angle accordingly. Those of ordinaryskill in the pertinent arts will recognize that the propellers of thepresent disclosure, including but not limited to the propeller 670 ofFIGS. 6A and 6B, may include any other mechanical and/or electricalsystems or operators (e.g., within the airfoils of the blade roots 672or blade tips 674) for changing cant angles with respect to the bladeroots 672, or for otherwise geometrically reconfiguring a propeller inaccordance with the present disclosure. Such systems or operators may beautomatically controlled using one or more blade controllers that may becontrolled by one or more computer processors residing aboard the aerialvehicle, or in a remote station or location, e.g., in a “cloud”-basedenvironment.

Additionally, in some embodiments, the blade tips 674 may alternativelybe provided with one or more biasing elements for urging the blade tips674 into a predetermined cant angle with respect to a corresponding oneof the blade roots 672. The blade tips 674 and/or the blade roots 674may be solid or substantially solid, and formed from one or morehomogenous or heterogeneous materials. Alternatively, the blade tips 674and/or the blade roots 672 may be substantially hollow, e.g., eachhaving a solid skin defining an airfoil having a hollow cavity therein,with one or more internal supports or structural features formaintaining a shape of the respective airfoils. For example, thepropeller 670 or portions thereof may be formed from durable frames ofstainless steel, carbon fibers or other similarly lightweight, rigidmaterials and reinforced with radially aligned fiber tubes or struts.Utilizing a propeller 670 having a substantially hollow cross-sectionthereby reduces the mass of the propeller 670, and enables wiring,cables and mechanical or electrical operators, e.g., one or morecomponents for varying a cant angle of a blade tip 674 with respect to ablade root 672, and in communication with one or more other controlsystems components or features. Some other mechanical or electricaloperators that may be utilized in accordance with the present disclosureinclude, but are not limited to, gear boxes, worm gears,servo-controlled arms. For example, mechanical or electrical equipmentthat is similar to equipment ordinarily utilized to change angles ofcontrol surfaces such as flaps, rudders or ailerons may be incorporatedinto the blade tips 674 and utilized to change the cant with respect tothe blade root 672. The propeller 670 or such portions thereof mayfurther be filled with foam or other fillers, strengthened with walls orother supports, and covered with flexible skins for resisting moisture,erosion or any other adverse effects of the elements.

In addition to varying cant angles of blade tips with respect to bladeroots, those of ordinary skill in the pertinent arts will recognize thata blade shape or geometry may be varied in any number of other ways.Referring to FIGS. 7A and 7B, views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the present disclosureare shown. Except where otherwise noted, reference numerals preceded bythe number “7” shown in FIGS. 7A and 7B indicate components or featuresthat are similar to components or features having reference numeralspreceded by the number “6” shown in FIGS. 6A and 6B, by the number “5”shown in FIGS. 5A through 5D, by the number “4” shown in FIGS. 4Athrough 4F, by the number “3” shown in FIG. 3, by the number “2” shownin FIG. 2 or by the number “1” shown in FIGS. 1A through 1F.

As is shown in FIGS. 7A and 7B, a propeller 770 includes a pair ofpropeller blades 772 mounted about a hub 780. Each of the blades 772includes an adjustable blade trailing edge 774 mounted at angles thatmay be modified during operation. For example, as is shown in FIG. 7A, ablade trailing edge 774 may be substantially coaligned with a blade 772,e.g., within a common plane of the blade 772. As is shown in FIG. 7B,however, the blade trailing edges 774 may be rotated about a hingedconnection and aligned at approximately ninety degree (90°) angles withrespect to the blades 772 by one or more mechanical or electricaloperators (not shown).

Referring to FIGS. 8A and 8B, views of aspects of an embodiment of apropulsion unit in accordance with embodiments of the present disclosureare shown. Except where otherwise noted, reference numerals preceded bythe number “8” shown in FIGS. 8A and 8B indicate components or featuresthat are similar to components or features having reference numeralspreceded by the number “7” shown in FIGS. 7A and 7B, by the number “6”shown in FIGS. 6A and 6B, by the number “5” shown in FIGS. 5A through5D, by the number “4” shown in FIGS. 4A through 4F, by the number “3”shown in FIG. 3, by the number “2” shown in FIG. 2 or by the number “1”shown in FIGS. 1A through 1F.

As is shown in FIGS. 8A and 8B, a propeller 870 includes threereconfigurable propeller blades 872 mounted about a hub 880. Each of theblades 872 includes an adjustable blade camber 874 provided at a widththat may be modified during operation. For example, as is shown in FIG.8A, the cambers 874 are shown as fully extended to a maximum width ofthe blades 872. As is shown in FIG. 8B, however, the cambers 874 arefully retracted within the blades 872 to a minimum width.

Those of ordinary skill in the pertinent arts will recognize that bladeshapes and/or geometries may be varied in any manner in accordance withthe present disclosure, including but not limited to varying cant anglesof blade tips, trailing edge angles and/or blade widths or otherdimensions, such as is shown in FIG. 6A, 6B, 7A, 7B, 8A or 8B, or in anyother manner, and that the propulsion units of the present disclosureare not limited to the embodiments of the propellers 670, 770, 870 shownin FIG. 6A, 6B, 7A, 7B, 8A or 8B.

As is discussed above, the various aspects of the propulsion units ofthe present disclosure may be independently operated in any number ofways in order to generate a specific force therefrom (e.g., lift and/orthrust), or to control a sound emitted thereby during operation (e.g., asound pressure level and/or frequency spectrum). For example, where aspecific position, velocity and/or acceleration is desired or requiredduring operation of an aerial vehicle having a plurality of propulsionunits of the present disclosure, each of the motor speeds, gimbalangles, blade pitch angles and/or blade shapes may be selectivelyadjusted in order to generate a net force in order to reach the desiredor required position or achieve the desired or required velocity oracceleration. Moreover, by selectively adjusting the motor speeds,gimbal angles, blade pitch angles and/or blade shapes, a net force forreaching the desired or required position, or for achieving the desiredor required velocity or acceleration, may be generated while emittingsounds in any number of different profiles or signatures.

Referring to FIGS. 9A through 9D, views of aspects of an aerial vehiclehaving one or more embodiments of propulsion units in accordance withembodiments of the present disclosure are shown. Except where otherwisenoted, reference numerals preceded by the number “9” shown in FIGS. 9Athrough 9D indicate components or features that are similar tocomponents or features having reference numerals preceded by the number“8” shown in FIGS. 8A and 8B, by the number “7” shown in FIGS. 7A and7B, by the number “6” shown in FIGS. 6A and 6B, by the number “5” shownin FIGS. 5A through 5D, by the number “4” shown in FIGS. 4A through 4F,by the number “3” shown in FIG. 3, by the number “2” shown in FIG. 2 orby the number “1” shown in FIGS. 1A through 1F.

As is shown in FIG. 9A, an aerial vehicle 910 includes four propulsionunits 930-1, 930-2, 930-3, 930-4 in operation. Each of the propulsionunits 930-1, 930-2, 930-3, 930-4 is generating a force F₁₋₁, F₂₋₁, F₃₋₁,F₄₋₁ that counteracts the weight ω₉₁₀ of the aerial vehicle 910. Each ofthe propulsion units 930-1, 930-2, 930-3, 930-4 includes a motorassembly 960-1, 960-2, 960-3, 960-4 and one or more actuators andcomponents for controlling the operation of the respective units 930-1,930-2, 930-3, 930-4 within housings thereof, and propellers 970-1,970-2, 970-3, 970-4 provided external to such housings. The motorassemblies 960-1, 960-2, 960-3, 960-4 and the propellers 970-1, 970-2,970-3, 970-4 of the present disclosure may be operated in order togenerate both the magnitudes and the directions of the forces F₁₋₁,F₂₋₁, F₃₋₁, F₄₋₁.

For example, as is shown in FIG. 9A, the propulsion unit 930-1 isoperated with the motor assembly 960-1 at a speed of 2100 revolutionsper minute (rpm), and at a gimbal angle ϕ₁₋₁ of zero degrees (0°), viz.,normal, and with blades of the propeller 970-1 at a pitch angle offifteen degrees (15°). Each of the linear actuators (not shown) withinthe propulsion unit 930-1 is extended at an equal distance of 1.2millimeters (mm), with such actuators determining both the gimbal angleand pitch angles. As a result of operating the propulsion unit 930-1 atthe speeds defined by the motor assembly 960-1, and the gimbal angle andpitch angles defined by the linear actuators (not shown), a force F₁₋₁having a value of ten pounds force (10 lbf) is generated in a directionof the gimbal angle ϕ₁₋₁. Sound N₁₋₁ at a sound pressure level ofeighty-two decibels (82 dB) is emitted from the propulsion unit 930-1.

As is also shown in FIG. 9A, the propulsion units 930-2, 930-3, 930-4are operated with the motor assemblies 960-2, 960-3, 960-4 at speeds of2200, 2225 and 2500 revolutions per minute (rpm), respectively, and atgimbal angles ϕ₂₋₁, ϕ₃₋₁, ϕ₄₋₁, of thirty-two degrees (32°), twelvedegrees (12°) and five degrees (5°), respectively, with blades of thepropellers 970-2, 970-3, 970-4 at pitch angles of twenty-five degrees(25°), ten degrees (10°) and ten degrees (10°), respectively. The linearactuators of the propulsion unit 930-2 are extended at distances of 1.9,1.0 and 0.9 millimeters (mm) each, respectively. The linear actuators ofthe propulsion unit 930-3 are extended at distances of 1.1, 1.2 and 1.2millimeters (mm), respectively. The linear actuators of the propulsionunit 930-4 are extended at distances of 1.1, 1.3 and 1.2 millimeters,respectively. The distances by which the linear actuators of thepropulsion units 930-2, 930-3, 930-4 are extended determine both thegimbal angles ϕ₂₋₁, ϕ₃₋₁, ϕ₄₋₁ of the propulsion units 930-2, 930-3,930-4, and the pitch angles of the blades of the propellers 970-2,970-3, 970-4. Therefore, as a result of operating the propulsion units930-2, 930-3, 930-4 at the speeds defined by the motor assemblies 960-2,960-3, 960-4, and the gimbal angles ϕ₂₋₁, ϕ₃₋₁, ϕ₄₋₁ and pitch anglesdefined by the linear actuators (not shown), forces F₂₋₁, F₃₋₁ and F₄₋₁having values of fourteen pounds force (14 lbf), eight pounds force (8lbf) and nine pounds force (9 lbf) are generated in directions of thegimbal angles ϕ₂₋₁, ϕ₃₋₁, ϕ₄₋₁, respectively. Sounds N₂₋₁, N₃₋₁, N₄₋₁ atsound pressure levels of eighty-four decibels (84 dB), eighty-ninedecibels (89 dB) and ninety-eight decibels (98 dB) are emitted from eachof the propulsion units 930-2, 930-3, 930-4, respectively.

As is shown in FIG. 9B, operation of the propulsion units 930-1, 930-2,930-3, 930-4 in the manner shown in FIG. 9A causes the aerial vehicle910 to travel at a velocity v₁ in a magnitude and a direction determinedbased at least in part on a net effect of each of the forces F₁₋₁, F₂₋₁,F₃₋₁, F₄₋₁ on the aerial vehicle 910 and the weight ω₉₁₀ of the aerialvehicle 910, as shown in FIG. 9A. The operation of the propulsion units930-1, 930-2, 930-3, 930-4 as shown in FIG. 9B further causes the aerialvehicle 910 to radiate a net sound N_(TOT-1).

As is also discussed above, where changing a position, a velocity and/oran acceleration of the aerial vehicle 910 is desired, the propulsionunits 930-1, 930-2, 930-3, 930-4 may be operated independently or inconcert to generate a net force on the aerial vehicle 910 that causesthe aerial vehicle 910 to travel to a different position, at a differentvelocity, or subject to a different acceleration. As is shown in FIG.9C, where discrete forces F₁₋₂, F₂₋₂, F₃₋₂, F₄₋₂ are desired or requiredfrom the propulsion units 930-1, 930-2, 930-3, 930-4, aspects of each ofthe propulsion units 930-1, 930-2, 930-3, 930-4, e.g., motor speeds,gimbal angles, blade pitch angles and/or blade shapes, may bemanipulated to enable the demand for the forces F₁₋₂, F₂₋₂, F₃₋₂, F₄₋₂from the propulsion units 930-1, 930-2, 930-3, 930-4.

For example, referring to FIG. 9C, the propulsion unit 930-1 is operatedwith the motor assembly 960-1 at a speed of 2359 revolutions per minute(rpm), and at a gimbal angle of fifty degrees (50°) and with blades ofthe propeller 970-1 at a pitch angle of twenty-two and one half degrees(22.5°). Two of the linear actuators (not shown) within the propulsionunit 930-1 are extended at distances of 1.7 millimeters (mm), while oneof the linear actuators is extended at a distance of 0.6 millimeters(mm), with such actuators determining both the gimbal angle and pitchangles. As a result of operating the propulsion unit 930-1 at the speedsdefined by the motor assembly 960-1, and the gimbal angle and pitchangles defined by the linear actuators (not shown), the force F₁₋₂having a value of eight-and-one-half pounds force (8.5 lbf) is generatedin a direction of the gimbal angle ϕ₁₋₂. Sound N₁₋₂ at a sound pressurelevel of ninety-one decibels (91 dB) is emitted from the propulsion unit930-1.

As is also shown in FIG. 9C, the propulsion units 930-2, 930-3, 930-4are operated with the motor assemblies 960-2, 960-3, 960-4 at speeds of1900, 2600 and 1950 revolutions per minute (rpm), respectively, and atgimbal angles ϕ₂₋₂, ϕ₃₋₂, ϕ₄₋₂ of twenty-one degrees (21°), eighteendegrees (18°) and zero degrees (0°), respectively, with blades of thepropellers 970-2, 970-3, 970-4 at pitch angles of fifteen degrees (15°),ten degrees (10°) and twenty degrees (20°), respectively. The linearactuators of the propulsion unit 930-2 are extended at distances of 1.1,1.5 and 1.3 millimeters (mm) each, respectively. The linear actuators ofthe propulsion unit 930-3 are extended at distances of 1.0, 1.0 and 1.0millimeters (mm), respectively. The linear actuators of the propulsionunit 930-4 are extended at distances of 1.3, 1.2 and 1.4 millimeters,respectively. The distances by which the linear actuators of thepropulsion units 930-2, 930-3, 930-4 are extended determine both thegimbal angles ϕ₂₋₂, ϕ₃₋₂, ϕ₄₋₂ of the propulsion units 930-2, 930-3,930-4, and the pitch angles of the blades of the propellers 970-2,970-3, 970-4. Therefore, as a result of operating the propulsion units930-2, 930-3, 930-4 at the speeds defined by the motor assemblies 960-2,960-3, 960-4, and the gimbal angles ϕ₂₋₂, ϕ₃₋₂, ϕ₄₋₂ and pitch anglesdefined by the linear actuators (not shown), the forces F₂₋₂, F₃₋₂ andF₄₋₂ having values of nine pounds force (9 lbf), thirteen pounds force(13 lbf) and eleven pounds force (11 lbf) are generated in directions ofthe gimbal angles ϕ₂₋₂, ϕ₃₋₂, ϕ₄₋₂, respectively. Sounds N₂₋₂, N₃₋₂,N₄₋₂ at sound pressure levels of seventy-seven decibels (77 dB),ninety-five decibels (95 dB) and seventy-eight decibels (78 dB) areemitted from each of the propulsion units 930-2, 930-3, 930-4,respectively.

As is shown in FIG. 9D, operation of the propulsion units 930-1, 930-2,930-3, 930-4 in the manner shown in FIG. 9C causes the aerial vehicle910 to travel at a velocity v₂ in a magnitude and a direction determinedbased at least in part on a net effect of each of the forces F₁₋₂, F₂₋₂,F₃₋₂, F₄₋₂ on the aerial vehicle 910 and the weight ω₉₁₀ of the aerialvehicle 910, as shown in FIG. 9C. The operation of the propulsion units930-1, 930-2, 930-3, 930-4 as shown in FIG. 9C further causes the aerialvehicle 910 to radiate a net sound N_(TOT-2).

Accordingly, those of ordinary skill in the pertinent arts willrecognize that the use of propulsion units with independently adjustableaspects on an aerial vehicle, such as the aerial vehicle 910 of FIGS. 9Athrough 9D, enables the aerial vehicle to selectively define not only amagnitude or direction of force (e.g., lift and/or thrust) but alsoaspects of the specific sounds (e.g., sound pressure levels and/orfrequency spectrums) generated thereby. For example, referring again tothe aerial vehicle 910 of FIGS. 9A through 9D, aspects of each of thepropulsion units 930-1, 930-2, 930-3, 930-4, e.g., motor speeds, gimbalangles, blade pitch angles and/or blade shapes, may be manipulated inorder to maintain the magnitude and direction of the forces generatedthereby constant, while varying the sound pressure levels and frequencyspectrums emitted during operation. In some embodiments, sounds that areemitted by an aerial vehicle may be monitored, and where such soundsapproach or exceed one or more thresholds, the sounds may be varied byindividually adjusting one or more aspects of the propulsion units930-1, 930-2, 930-3, 930-4.

As is discussed above, aspects of embodiments of the propulsion units ofthe present disclosure may be independently manipulated to generateforces thereby, and such forces may have a net effect on an aerialvehicle outfitted with such propulsion units. Thus, the individualaspects of such propulsion units may be individually selected togenerate specific forces from each of such propulsion units which, whenaggregated, impart a desired net force upon the aerial vehicle as awhole. In some other embodiments, such aspects may be individuallyselected as a part of an overall sound management strategy, e.g., tolimit or confine sound pressure levels and/or frequency spectrumsradiating from a propulsion unit individually, or by an aerial vehicleas a whole, during operation.

Referring to FIG. 10, a flow chart 1000 of one process for operating anaerial vehicle having one or more embodiments of propulsion units inaccordance with the present disclosure is shown. At box 1010, a desiredthrust vector for a propulsion unit on an aerial vehicle is determined.For example, the desired thrust vector may be selected in order to causethe aerial vehicle to travel to a specific point, or at a desiredvelocity, or subject to a specific acceleration. The desired thrustvector may also be selected based on one or more operating restrictions(e.g., speeds, altitudes, levels of sound or noise, maneuverability,fuel efficiency and/or battery life) or environmental conditions (e.g.,adverse weather conditions or air or ground traffic). In someembodiments, the desired thrust vector for the propulsion unit will beselected in concert with desired thrust vectors for one or more otherpropulsion units provided on the aerial vehicle.

At box 1020, a noise restriction associated with the operation of theaerial vehicle and or the propulsion unit in an environment isidentified. For example, the noise restriction may identify an expresslyset limit on sound pressure levels (or intensities), or on frequencyspectrums, that may be radiated from the aerial vehicle or thepropulsion unit. Alternatively, the noise restriction may be a generalrestriction, e.g., based on safe hearing standards of humans or otheranimals within the environment, or a time-based limit, e.g., operatingmachinery when humans or other animals are expected to be sleepingwithin the environment. At box 1030, operational characteristics (e.g.,a motor speed, a propeller blade pitch, a gimbal angle and/or a bladeshape) that are required for the propulsion unit to achieve the thrustvector and satisfy the noise restriction are selected. For example, asis discussed above, a given force (e.g., a magnitude and a direction)may be provided by a propulsion unit in accordance with the presentdisclosure in any number of combinations of operational characteristics.For example, the same thrust may be provided when a propeller rotates ata first speed and with a first blade pitch angle, or at a second speedand with a second blade pitch angle. A propulsion unit may be operatedin many combinations of such aspects in order to obtain the same forcetherefrom, and each of such combinations may cause the propulsion unitto radiate sound with different sound pressure levels, or withindifferent frequency spectrums. Therefore, a combination of operationalcharacteristics of the propulsion units that causes the propulsion unitto generate the desired thrust vector, and radiate sounds that satisfythe noise restriction, may be selected.

At box 1040, a motor is operated at a motor speed selected at box 1030.For example, in some embodiments, one or more signals may be provided toan electronic speed control (or ESC) for controlling the angularvelocity of a motor provided in association with the propulsion unit. Atbox 1050, one or more linear actuators are operated in order to placeblades of a propeller associated with the propulsion unit at a pitchangle selected at box 1030, and at box 1060, the one or more linearactuators are operated in order to place the propeller at a gimbal angleselected at box 1030. For example, in accordance with some embodimentsof the present disclosure, such as the propulsion unit 130-4 shown inFIGS. 1B, 1C and 1F or the propulsion unit 330 shown in FIG. 3, thelinear actuators may be operated separately or simultaneously, and tocommon or different extents, in order to change a relative position ororientation of a plate element, and to impart a desired gimbal angleupon the propeller, or a desired pitch angle upon one or more blades ofthe propeller. At box 1070, a blade controller is operated to implementa blade shape selected at box 1030, and the process ends. The bladecontroller may change the shapes or dimensions of one or more blades ofa propeller provided in association with the propulsion unit, in auniform or disparate manner, thereby causing the propeller to bebalanced or imbalanced, as desired.

Accordingly, where a force is desired or required from a propulsion unitin accordance with the present disclosure, that force may be selectivelygenerated, subject to the operational capacities of the propulsion unit,by varying one or more aspects of the propulsion unit such as motorspeeds, gimbal angles, blade pitch angles or blade shapes. Moreover, if,after a desired magnitude and direction of thrust is obtained inaccordance with the process shown in the flow chart 1000 of FIG. 10, adifferent thrust vector is desired, then one or more of the aspects ofthe propulsion unit may be modified accordingly in order to achieve athrust consistent with that desired thrust vector. Furthermore, thevalues or levels of such aspects may be selected, subject to theoperational capacities of the propulsion unit, with sounds generated bythe propulsion unit in mind. For example, where the same level ordirection of thrust may be obtained at two different motor speeds orwith two different gimbal angles, blade pitch angles or blade shapes, acombination of motor speed, gimbal angle, blade pitch angle and/or bladeshape that results in a lowest sound pressure level, or a more favorablefrequency spectrum, may be selected, and a propulsion unit may beoperated accordingly.

In accordance with the present disclosure, a propulsion unit may beselectively monitored in operation with respect to the sound radiatedtherefrom, and aspects of the propulsion unit may be modified, e.g.,either separately or in parallel, during operation in order to change asound pressure level, or a frequency spectrum, of the radiated sound asnecessary. Referring to FIG. 11, a flow chart 1100 of one process foroperating an aerial vehicle having one or more embodiments of propulsionunits in accordance with the present disclosure is shown. At box 1110, apropulsion unit is operated with a motor at an initial speed, and with apropeller at an initial pitch, an initial gimbal angle and an initialshape. For example, referring again to FIG. 9A, one or more of thepropulsion units 930-1, 930-2, 930-3, 930-4 may operate in accordancewith one or more of the sets of aspects or operational characteristicsshown thereon.

At box 1120, information regarding the operation of the propulsion unitand/or the aerial vehicle and any observed noise is captured using oneor more sensors onboard the aerial vehicle. For example, such sensorsmay include position sensors (e.g., a GPS sensors), velocity sensors(e.g., speedometers or air speed indicators), acceleration sensors(e.g., accelerometers) or orientations sensors (e.g., gyroscopes orcompasses). Such sensors may further include one or more altimeters,barometers, range finders, air monitoring sensors or imaging devices.Additionally, such sensors may also include one or more microphones,piezoelectric sensors or vibration sensors.

At box 1130, the noises observed at box 1120 are compared to a desirednoise to be emitted by the propeller during operation. For example,where the aerial vehicle is expected to operate in a specificenvironment, a library or index of desired noises may be consulted toidentify whether any specific noises are preferred or desired for thatlocation. Alternatively, a desired noise may be defined in the negative,e.g., a noise that is below thresholds of sound pressure level or withina predefined frequency spectrum, or subject to one or more restrictionsbased on a time, a location, or a particular environment.

At box 1140, whether the noise observed at box 1120 is consistent withthe desired noise is determined. If the observed noise is consistentwith the desired noise, then the process ends. If the observed noise isnot consistent with the desired noise, then the process advances to box1150, where differences between the observed noise and the desired noiseare identified. Such differences may relate to discrete narrow bandtonals, or a broadband frequency spectrum, that are present or lackingwithin either the observed noise or the desired noise, or sound pressurelevels or frequency spectrums of either the observed noise or thedesired noise.

At box 1160, a modified motor speed, a modified pitch, a modified gimbalangle and/or a modified blade shape are selected based on thedifferences between the observed noise and the desired noise. Forexample, a motor speed that is expected to change the sound pressurelevel or the frequency spectrum of the sounds radiated from thepropulsion unit during operation may be determined. Likewise, a positionof one or more linear actuators in order to change a gimbal angle and/orblade pitch of the propeller may also be determined. Moreover, aspecific blade shape (e.g., a cant angle of a blade tip, or a shape ofthe blade) may also be determined.

Once changes to one or more aspects or operational characteristics ofthe propulsion unit are identified, such changes may be implementedeither in series or in parallel. At box 1170, the motor is operated atthe modified motor speed, e.g., by sending one or more control signalsto an electronic speed control of the motor, and increasing ordecreasing the motor speed accordingly. At box 1172, the linearactuators are operated to establish the modified pitch angle, and at box1172, the linear actuators are operated to establish the modified gimbalangle, e.g., by varying a relative position or angular orientation of aplate element associated with one or more aspects of the propeller, suchas is discussed above with regard to FIG. 3, 4A through 4F or 5A through5D, or in any other manner. At box 1176, one or more blade controllersare operated to establish a modified blade shape.

After the changes to the one or more aspects or operationalcharacteristics of the propulsion unit are identified and implemented,the process returns to box 1120, where information regarding theoperation of the propulsion unit with the modified aspects oroperational characteristics and/or the aerial vehicle and any observednoise is captured using one or more sensors onboard the aerial vehicle.The operation of the propulsion unit and/or the aerial vehicle may becontinuously monitored until an observed noise is consistent with adesired noise, or until the aerial vehicle arrives at a destination, inaccordance with the present disclosure.

In accordance with systems and methods of the present disclosure, suchas the process represented in the flow chart 1100 of FIG. 11, it is notnecessary to modify each of the adjustable aspects or operationalcharacteristics of a propulsion unit in order to change a magnitude or adirection of a force generated thereby. Rather, where a desired changein a magnitude or a direction of a force generated by a propulsion unitmay be effected by changing only one of a motor speed, a gimbal angle, ablade pitch angle or a blade shape, or by changing fewer than all of themotor speed, the gimbal angle, the blade pitch angle or the blade shape,then only such aspects need be changed. For example, referring again tothe flow chart 1100 of FIG. 11, one or more of the actions or stepsassociated with boxes 1170, 1172, 1174, 1176 may be bypassed if suchactions or steps are not required in order for a propulsion unit togenerate a force at a desired magnitude and direction, or in order tooperate the propulsion unit at a desired sound pressure level or withina desired frequency spectrum. Moreover, such processes may be performedindependently or in parallel for each of the propulsion units providedon an aerial vehicle, as necessary, in order to impart a net forcehaving a desired magnitude or direction, or to radiate sounds therefromat a desired sound pressure level or within a desired frequencyspectrum.

Those of ordinary skill in the pertinent art will further recognize thatthe systems and methods of the present disclosure may be utilized toplan for and track the operation of one or more propulsion units, andthe sounds radiating therefrom, during operation. For example, where anaerial vehicle is configured with one or more of the propulsion units ofthe present disclosure, and is intended to perform a mission orevolution requiring travel from an origin to a destination, and/orthrough one or more intervening waypoints, various aspects oroperational characteristics of such propulsion units may be selected inadvance in accordance with a transit plan for the mission or evolution,such that the aspects or operational characteristics may be modifiedupon the aerial vehicle's arrival at one or more of the interveningwaypoints or when the aerial vehicle encounters one or moreenvironmental conditions. The aspects or operational characteristics ofthe propulsion units during operation may be further selected on anybasis, e.g., a measure or rating of the thrust capacity, the liftcapacity or the speed capacity that may be provided by the propulsionunits, a measure or rating of the maneuverability of an aerial vehiclewhile operating the propulsion units, or a measure or rating of the oneor more sounds that may be emitted by the propulsion units duringoperation. Such aspects or operational characteristics may also beselected based on a general level or degree of performance, or on alevel or degree of performance in specific instances, e.g., with regardto specific goals or objectives such as maneuverability, fuel efficiencyand/or battery life, or adverse weather conditions.

Referring to FIG. 12, a flow chart 1200 of one process for operating anaerial vehicle having one or more embodiments of propulsion units inaccordance with the present disclosure is shown. At box 1210, a transitplan for a transit of an aerial vehicle from an origin to a destinationhaving a plurality of stages is identified. For example, the transitplan may comprise information regarding a mission to be performed by theaerial vehicle, including but not limited to dates or times at which theaerial vehicle is to depart from or arrive at an origin, a destination,or one or more intervening waypoints, or actions or evolutions to beperformed by the aerial vehicle at the origin, at the destination, or atthe waypoints, or while in transit.

At box 1220, operational characteristics of the aerial vehicle duringthe transit in accordance with the transit plan, e.g., courses or speedsof the aerial vehicle, and corresponding instructions to be provided tosuch motors, rotors, rudders, ailerons, flaps or other features of theaerial vehicle in order to achieve such courses or speeds, arepredicted. At box 1230, environmental conditions to be encountered bythe aerial vehicle during the transit in accordance with the transitplan are predicted. For example, weather forecasts for the times ordates of the departure or the arrival of the aerial vehicle, and for thelocations of the origin or the destination, may be identified on anybasis.

At box 1240, sound pressure levels and/or frequency spectrums ofpreferred sounds to be emitted by the aerial vehicle during the transitare determined based at least in part on the transit plan identified atbox 1210, the operational characteristics (e.g., courses, speeds, lift,thrust, maneuverability, efficiency) predicted at box 1220, or theenvironmental conditions (e.g., temperatures, pressures, humidities,wind speeds, directions, measures of cloud coverage, sunshine, orsurface conditions or textures of an environment between and includingthe origin and the destination) predicted at box 1230. For example,information or data regarding the transit plan, the predictedoperational characteristics or the predicted environmental conditionsmay be provided to a trained machine learning system as initial inputs.The machine learning system may utilize one or more algorithms ortechniques such as nearest neighbor methods or analyses, factorizationmethods or techniques, K-means clustering analyses or techniques,similarity measures such as log likelihood similarities or cosinesimilarities, latent Dirichlet allocations or other topic models, orlatent semantic analyses, and may be trained to select preferred soundpressure levels and/or frequency spectrums to be emitted during one ormore stages of the transit plan, or as the aerial vehicle operates inaccordance with the predicted operating characteristics or within thepredicted environmental conditions. In some embodiments, the trainedmachine learning system resides and/or operates on one or more computingdevices or machines provided onboard the aerial vehicle. In some otherembodiments, the trained machine learning system resides in one or morealternate or virtual locations, e.g., in a “cloud”-based environmentaccessible via a network.

At box 1250, one or more of a motor speed, a blade pitch, a gimbal angleand/or a blade shape is selected for each stage of the transit planbased at least in part on the sound pressure levels and/or frequencyspectrums of the preferred sounds to be emitted by the aerial vehicleduring operation. For example, a schedule or list of computer-executableinstructions to be provided to a motor, to one or more linear actuatorsor to one or more blade controllers may be defined and stored in one ormore data stores, e.g., onboard the aerial vehicle or in one or moreexternal, accessible locations. In some embodiments, the instructionsmay be executed at a predetermined time, or when the aerial vehiclearrives at a predetermined location. In some other embodiments, theinstructions may be executed when the aerial vehicle encounters apredetermined environmental condition, when the aerial vehicle reachesan operational milestone or upon an occurrence of a predetermined event.At box 1260, a motor, one or more linear actuators and/or one or moreblade controllers are operated to emit the preferred sounds during eachstage of the transit plan, and the process ends.

Although the disclosure has been described herein using exemplarytechniques, components, and/or processes for implementing the systemsand methods of the present disclosure, it should be understood by thoseskilled in the art that other techniques, components, and/or processesor other combinations and sequences of the techniques, components,and/or processes described herein may be used or performed that achievethe same function(s) and/or result(s) described herein and which areincluded within the scope of the present disclosure.

Those of ordinary skill in the pertinent arts will recognize that thepropulsion units of the present disclosure may include any number ofmotors of any type, as well as any number of propellers of any type(e.g., propellers having any number of blades of any size or shape), anynumber of actuators for modifying gimbal angles or blade pitch angles,or any number of blade controllers for modifying blade shapes. Moreover,those of ordinary skill in the pertinent arts will further recognizethat an aerial vehicle may include any number of the propulsion units ofthe present disclosure.

For example, those of ordinary skill in the pertinent arts will alsorecognize that the systems and methods disclosed herein may be utilizedin connection with any type or form of aerial vehicle (e.g., manned orunmanned) having fixed or rotating wings and having any intendedindustrial, commercial, recreational or other use. In particular,although some of the embodiments disclosed herein reference propellershaving two blades or four blades, or aerial vehicles having fourpropulsion units having one motor and one propeller each, those ofordinary skill in the pertinent arts will recognize that the systems andmethods of the present disclosure may be utilized in connection withpropellers having any number of blades, and in connection with aerialvehicles having any number of propulsion units with any number of motorsor propellers (e.g., for redundancy). Moreover, although some of theembodiments disclosed herein reference the use of propellers on aerialvehicles, those of ordinary skill in the pertinent arts will recognizethat the systems and methods of the present disclosure may be utilizedin connection with seagoing vessels, as well.

Furthermore, those of ordinary skill in the pertinent arts willrecognize that the systems and methods disclosed herein may be used tocause an aerial vehicle to radiate sounds at predetermined soundpressure levels and/or within predetermined frequency spectrums. Bycontrolling the operation of a plurality of propulsion units, e.g., byindividually controlling motor speeds, gimbal angles, blade pitch anglesor blade shapes of such units, an aerial vehicle may effectively emit aspecific sound, as desired, while meeting a demand for force (e.g.,thrust and/or lift).

It should be understood that, unless otherwise explicitly or implicitlyindicated herein, any of the features, characteristics, alternatives ormodifications described regarding a particular embodiment herein mayalso be applied, used, or incorporated with any other embodimentdescribed herein, and that the drawings and detailed description of thepresent disclosure are intended to cover all modifications, equivalentsand alternatives to the various embodiments as defined by the appendedclaims. Moreover, with respect to the one or more methods or processesof the present disclosure described herein, including but not limited tothe processes represented in the flow charts of FIGS. 10 through 12,orders in which such methods or processes are presented are not intendedto be construed as any limitation on the claimed inventions, and anynumber of the method or process steps or boxes described herein can becombined in any order and/or in parallel to implement the methods orprocesses described herein. Also, the drawings herein are not drawn toscale.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey in apermissive manner that certain embodiments could include, or have thepotential to include, but do not mandate or require, certain features,elements and/or steps. In a similar manner, terms such as “include,”“including” and “includes” are generally intended to mean “including,but not limited to.” Thus, such conditional language is not generallyintended to imply that features, elements and/or steps are in any wayrequired for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements and/or steps are included orare to be performed in any particular embodiment.

Disjunctive language such as the phrase “at least one of X, Y, or Z,” or“at least one of X, Y and Z,” unless specifically stated otherwise, isotherwise understood with the context as used in general to present thatan item, term, etc., may be either X, Y, or Z, or any combinationthereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is notgenerally intended to, and should not, imply that certain embodimentsrequire at least one of X, at least one of Y, or at least one of Z toeach be present.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C.

Language of degree used herein, such as the terms “about,”“approximately,” “generally,” “nearly” or “substantially” as usedherein, represent a value, amount, or characteristic close to the statedvalue, amount, or characteristic that still performs a desired functionor achieves a desired result. For example, the terms “about,”“approximately,” “generally,” “nearly” or “substantially” may refer toan amount that is within less than 10% of, within less than 5% of,within less than 1% of, within less than 0.1% of, and within less than0.01% of the stated amount.

Although the invention has been described and illustrated with respectto illustrative embodiments thereof, the foregoing and various otheradditions and omissions may be made therein and thereto withoutdeparting from the spirit and scope of the present disclosure.

What is claimed is:
 1. An aerial vehicle comprising: a first propulsionunit comprising a first gimbaling mechanism and a first motor assemblycomprising a first propulsion motor and a first propeller rotatablycoupled to the first propulsion motor by a first drive shaft, whereinthe first motor assembly is pivotably joined to the first gimbalingmechanism, wherein the first drive shaft defines a first axis, andwherein the first motor assembly is configured to rotate the firstpropeller about the first axis; a second propulsion unit comprising asecond gimbaling mechanism and a second motor assembly comprising asecond propulsion motor and a second propeller rotatably coupled to thesecond propulsion motor by a second drive shaft, wherein the secondmotor assembly is pivotably joined to the second gimbaling mechanism,wherein the second drive shaft defines a second axis, and wherein thesecond motor assembly is configured to rotate the second propeller aboutthe second axis; and a computing device having a memory and one or morecomputer processors, wherein the computing device is in communicationwith the first propulsion motor and the second propulsion motor, andwherein the computing device is configured to at least: select at leastone of a first course, a first air speed or a first altitude for theaerial vehicle; determine a first force to be supplied by the firstpropulsion unit and a second force to be supplied by the secondpropulsion unit in order for the aerial vehicle to operate in accordancewith the at least one of the first course, the first air speed or thefirst altitude; select a first rotational speed of the first propellerand a first gimbal angle of the first shaft based at least in part onthe first force; cause the first propulsion motor to rotate the firstpropeller at the first rotational speed; cause the first gimbalingassembly to align the first shaft at the first gimbal angle; select asecond rotational speed of the second propeller and a second gimbalangle of the second shaft based at least in part on the second force;cause the second propulsion motor to rotate the second propeller at thesecond rotational speed; and cause the second gimbaling assembly toalign the second shaft at the second gimbal angle.
 2. The aerial vehicleof claim 1, wherein the computing device is further configured to atleast: with the first propulsion motor rotating the first propeller atthe first rotational speed and the second propulsion motor rotating thesecond propeller at the second rotational speed, determine that theaerial vehicle is operating at at least one of a second course, a secondspeed or a second altitude; determine at least a third force to besupplied by the first propulsion unit in order for the unmanned aerialvehicle to return to the at least one of the first course, the first airspeed or the first altitude; select at least one of a third rotationalspeed of the first propeller or a third gimble angle of the first shaftbased at least in part on the third force; and at least one of: causethe first propulsion motor to rotate the first propeller at the thirdrotational speed; or cause the first gimbaling assembly to align thefirst shaft at the third gimbal angle.
 3. The aerial vehicle of claim 1,wherein the first altitude is the second altitude, wherein the firstspeed is zero, and wherein the second speed is zero.
 4. The aerialvehicle of claim 1, wherein the computing device is further configuredto at least: determine a position of the aerial vehicle; determine atleast one noise constraint associated with the position of the aerialvehicle, wherein the at least one noise constraint comprises at leastone of a sound pressure level limit or a frequency spectrum limit withinthe vicinity of the aerial vehicle; and determining at least one of thefirst rotational speed or the second rotational speed based at least inpart on the at least one noise constraint.
 5. A method for operating anaerial vehicle, wherein the aerial vehicle comprises a first propulsionunit having a first motor comprising a first drive shaft and a firstpropeller rotatably coupled to the first drive shaft, and wherein themethod comprises: identifying at least one of a first course, a firstair speed or a first altitude for the aerial vehicle; determining afirst force to be generated by the first propulsion unit to cause theaerial vehicle to travel on the first course, at the first air speed orat the first altitude, wherein the first force comprises a firstmagnitude and a first direction; determining at least a first motorspeed to generate the first magnitude of the first force; aligning thefirst drive shaft in a first angular orientation associated with thefirst direction of the first force; and operating the first motor at thefirst motor speed.
 6. The method of claim 5, wherein the firstpropulsion unit further comprises: a first plate element having a firstbore, wherein the first plate element defines a first plane, wherein thefirst bore is substantially perpendicular to the first plane, andwherein the first drive shaft extends through the first bore; and afirst gimbaling base, wherein the first motor is pivotably joined to thefirst gimbaling base, and wherein the first gimbaling base enables anangular orientation of the first drive shaft to vary within apredetermined angular range.
 7. The method of claim 6, wherein the firstpropeller further comprises a first variable pitch hub and a firstplurality of blades pivotably joined to the first variable pitch hub,and wherein a pitch angle of each of the first plurality of blades isdefined based at least in part on a relative position of the firstvariable pitch hub with respect to the first plate element.
 8. Themethod of claim 7, wherein determining at least the first motor speed togenerate the first magnitude of the first force further comprises:determining a first pitch angle for each of the first plurality ofblades to generate the first magnitude of the first force; determining afirst relative position of the first plate element with respect to thefirst variable pitch hub for placing each of the plurality of blades ofthe propeller at the first pitch angle; and causing the first plateelement to be placed at the first relative position with respect to thefirst variable pitch hub.
 10. The method of claim 8, wherein the firstpropulsion unit further comprises: a first plate support extendingbetween a first portion of the first gimbaling base and a first portionof the first plate element; and a first actuator configured to increaseor decrease a distance between the first portion of the first gimbalingbase and the first portion of the first plate element, wherein causingthe first plate element to be placed at the first relative position withrespect to the first variable pitch hub further comprises: determining afirst distance between the first portion of the first plate element andthe first portion of the first gimbaling base, wherein the firstdistance is associated with the first relative position; and causing thefirst portion of the first plate element to be placed at the firstdistance from the first portion of the first gimbaling base by the firstactuator.
 11. The method of claim 10, wherein the first plate supportfurther comprises a first support shaft, a first ball joint and a firstknuckle joint, wherein the first support shaft is joined to the firstportion of the plate element by the first ball joint, wherein the firstsupport shaft is joined to the first portion of the first gimbaling baseby the first knuckle joint, and wherein the first actuator is configuredto increase or decrease the distance between the first portion of thefirst gimbaling base and the first portion of the plate element byincreasing or decreasing a length of the first support shaft.
 12. Themethod of claim 8, wherein determining at least the first motor speed togenerate the first magnitude of the first force comprises: identifyingat least one noise constraint associated with operation of the aerialvehicle, wherein the at least one noise constraint comprises at leastone of a sound pressure level limit within a vicinity of the area of theaerial vehicle or a frequency spectrum limit within the vicinity of theaerial vehicle; and determining at least one of the first motor speed orthe first pitch angle based at least in part on the at least one noiseconstraint.
 13. The method of claim 7, wherein determining at least thefirst motor speed to generate the first magnitude of the first forcefurther comprises: determining a first shape of at least one of thefirst plurality of blades to generate the first magnitude of the firstdesired force, and wherein the method further comprises: causing the atleast one of the first plurality of blades to have the first shape. 14.The method of claim 5, further comprising: with the first motoroperating at the first motor speed, determining that the aerial vehicleis traveling on a second course, at a second air speed or at a secondaltitude; determining a second force to be generated by the firstpropulsion unit to cause the aerial vehicle to return to the at leastone of the first course, the first air speed or the first altitude,wherein the second force comprises a second magnitude and a seconddirection; determining a second motor speed to generate the secondmagnitude of the second force; aligning the second drive shaft in asecond angular orientation associated with the second direction of thesecond force; and operating the second motor at the second motor speed.15. The method of claim 14, further comprising: wherein the firstaltitude is the second altitude, wherein the first air speed is zero,and wherein the second air speed is zero.
 16. The method of claim 5,further comprising: with the first motor operating at the first motorspeed, identifying at least one of a second course, at a second airspeed or a second altitude for the aerial vehicle; determining a secondforce to be generated by the first propulsion unit to cause the aerialvehicle to travel on the first course, at the first air speed or at thefirst altitude, wherein the second force comprises a second magnitudeand a second direction; determining a second motor speed to generate thesecond magnitude of the second force; aligning the second drive shaft ina second angular orientation associated with the second direction of thesecond force; and operating the first motor at the second motor speed.17. The method of claim 5, wherein the aerial vehicle comprises a secondpropulsion unit having a second motor comprising a second drive shaftand a second propeller rotatably coupled to the second drive shaft, andwherein the method further comprises: determining a first net forcerequired to cause the aerial vehicle to travel on the first course, atthe first air speed or at the first altitude, wherein the first netforce is a sum of the first force and a second force to be generated bythe second propulsion unit, and wherein the second force comprises asecond magnitude and a second direction; determining at least a secondmotor speed to generate the second magnitude of the second force; andaligning the second drive shaft in a second angular orientationassociated with the second direction of the second force, and whereinoperating the second motor at the second motor speed comprises:operating the second motor at the second motor speed.
 18. A propulsionunit comprising: a base comprising a gimbaling mechanism; a plateelement comprising a bore aligned substantially perpendicular to a planeof the plate element; and a plate support extending between a portion ofthe base and a portion of the plate element, wherein the plate supportcomprises: a shaft; a ball joint joining an end of the shaft to theportion of the plate element; a knuckle joint joining a second end ofthe shaft to the portion of the base; and an actuator configured toincrease or decrease a length of the shaft.
 19. The propulsion unit ofclaim 18, wherein the plane of the plate element is provided at a firstplanar angle at a first time, and wherein the propulsion unit furthercomprises at least one computer processor configured to execute one ormore computer instructions for performing a method comprising: selectinga desired angle of orientation for the bore at a second time;determining a second planar angle of the plane of the plate elementcorresponding to the desired angle of orientation; determining a changein the length associated with the second planar angle of the plane ofthe plate element; and causing the change in the length by the actuatorafter the first time and prior to the second time.
 20. The propulsionunit of claim 18, further comprising: a propulsion motor having a driveshaft slidably inserted through the bore, wherein the propulsion motoris pivotably mounted to the gimbaling mechanism, and wherein the driveshaft is aligned substantially perpendicular to the plane of the plateelement.